code: import torch, torchvision
  import torch.nn as nn
  import torch.nn.functional as F
  from torchvision.models.resnet import Bottleneck
  import numpy as np
  from itertools import product
  from math import sqrt
  from typing import List
  from collections import defaultdict
  
  from data.config import cfg, mask_type
  from layers import Detect
  from layers.interpolate import InterpolateModule
  from backbone import construct_backbone
  
  import torch.backends.cudnn as cudnn
  from utils import timer
  from utils.functions import MovingAverage, make_net
  
  # This is required for Pytorch 1.0.1 on Windows to initialize Cuda on some driver versions.
  # See the bug report here: https://github.com/pytorch/pytorch/issues/17108
  torch.cuda.current_device()
  
  # As of March 10, 2019, Pytorch DataParallel still doesn't support JIT Script Modules
  use_jit = torch.cuda.device_count() <= 1
  if not use_jit:
      print('Multiple GPUs detected! Turning off JIT.')
  
  ScriptModuleWrapper = torch.jit.ScriptModule if use_jit else nn.Module
  script_method_wrapper = torch.jit.script_method if use_jit else lambda fn, _rcn=None: fn
  
  
  
  class Concat(nn.Module):
      def __init__(self, nets, extra_params):
          super().__init__()
  
          self.nets = nn.ModuleList(nets)
          self.extra_params = extra_params
      
      def forward(self, x):
          # Concat each along the channel dimension
          return torch.cat([net(x) for net in self.nets], dim=1, **self.extra_params)
  
  prior_cache = defaultdict(lambda: None)
  
  class PredictionModule(nn.Module):
      """
      The (c) prediction module adapted from DSSD:
      https://arxiv.org/pdf/1701.06659.pdf
  
      Note that this is slightly different to the module in the paper
      because the Bottleneck block actually has a 3x3 convolution in
      the middle instead of a 1x1 convolution. Though, I really can't
      be arsed to implement it myself, and, who knows, this might be
      better.
  
      Args:
          - in_channels:   The input feature size.
          - out_channels:  The output feature size (must be a multiple of 4).
          - aspect_ratios: A list of lists of priorbox aspect ratios (one list per scale).
          - scales:        A list of priorbox scales relative to this layer's convsize.
                           For instance: If this layer has convouts of size 30x30 for
                                         an image of size 600x600, the 'default' (scale
                                         of 1) for this layer would produce bounding
                                         boxes with an area of 20x20px. If the scale is
                                         .5 on the other hand, this layer would consider
                                         bounding boxes with area 10x10px, etc.
          - parent:        If parent is a PredictionModule, this module will use all the layers
                           from parent instead of from this module.
      """
      
      def __init__(self, in_channels, out_channels=1024, aspect_ratios=[[1]], scales=[1], parent=None, index=0):
          super().__init__()
  
          self.num_classes = cfg.num_classes
          self.mask_dim    = cfg.mask_dim # Defined by Yolact
          self.num_priors  = sum(len(x)*len(scales) for x in aspect_ratios)
          self.parent      = [parent] # Don't include this in the state dict
          self.index       = index
          self.num_heads   = cfg.num_heads # Defined by Yolact
  
          if cfg.mask_proto_split_prototypes_by_head and cfg.mask_type == mask_type.lincomb:
              self.mask_dim = self.mask_dim // self.num_heads
  
          if cfg.mask_proto_prototypes_as_features:
              in_channels += self.mask_dim
          
          if parent is None:
              if cfg.extra_head_net is None:
                  out_channels = in_channels
              else:
                  self.upfeature, out_channels = make_net(in_channels, cfg.extra_head_net)
  
              if cfg.use_prediction_module:
                  self.block = Bottleneck(out_channels, out_channels // 4)
                  self.conv = nn.Conv2d(out_channels, out_channels, kernel_size=1, bias=True)
                  self.bn = nn.BatchNorm2d(out_channels)
  
              self.bbox_layer = nn.Conv2d(out_channels, self.num_priors * 4,                **cfg.head_layer_params)
              self.conf_layer = nn.Conv2d(out_channels, self.num_priors * self.num_classes, **cfg.head_layer_params)
              self.mask_layer = nn.Conv2d(out_channels, self.num_priors * self.mask_dim,    **cfg.head_layer_params)
              
              if cfg.use_mask_scoring:
                  self.score_layer = nn.Conv2d(out_channels, self.num_priors, **cfg.head_layer_params)
  
              if cfg.use_instance_coeff:
                  self.inst_layer = nn.Conv2d(out_channels, self.num_priors * cfg.num_instance_coeffs, **cfg.head_layer_params)
              
              # What is this ugly lambda doing in the middle of all this clean prediction module code?
              def make_extra(num_layers):
                  if num_layers == 0:
                      return lambda x: x
                  else:
                      # Looks more complicated than it is. This just creates an array of num_layers alternating conv-relu
                      return nn.Sequential(*sum([[
                          nn.Conv2d(out_channels, out_channels, kernel_size=3, padding=1),
                          nn.ReLU(inplace=True)
                      ] for _ in range(num_layers)], []))
  
              self.bbox_extra, self.conf_extra, self.mask_extra = [make_extra(x) for x in cfg.extra_layers]
              
              if cfg.mask_type == mask_type.lincomb and cfg.mask_proto_coeff_gate:
                  self.gate_layer = nn.Conv2d(out_channels, self.num_priors * self.mask_dim, kernel_size=3, padding=1)
  
          self.aspect_ratios = aspect_ratios
          self.scales = scales
  
          self.priors = None
          self.last_conv_size = None
          self.last_img_size = None
  
      def forward(self, x):
          """
          Args:
              - x: The convOut from a layer in the backbone network
                   Size: [batch_size, in_channels, conv_h, conv_w])
  
          Returns a tuple (bbox_coords, class_confs, mask_output, prior_boxes) with sizes
              - bbox_coords: [batch_size, conv_h*conv_w*num_priors, 4]
              - class_confs: [batch_size, conv_h*conv_w*num_priors, num_classes]
              - mask_output: [batch_size, conv_h*conv_w*num_priors, mask_dim]
              - prior_boxes: [conv_h*conv_w*num_priors, 4]
          """
          # In case we want to use another module's layers
          src = self if self.parent[0] is None else self.parent[0]
          
          conv_h = x.size(2)
          conv_w = x.size(3)
          
          if cfg.extra_head_net is not None:
              x = src.upfeature(x)
          
          if cfg.use_prediction_module:
              # The two branches of PM design (c)
              a = src.block(x)
              
              b = src.conv(x)
              b = src.bn(b)
              b = F.relu(b)
              
              # TODO: Possibly switch this out for a product
              x = a + b
  
          bbox_x = src.bbox_extra(x)
          conf_x = src.conf_extra(x)
          mask_x = src.mask_extra(x)
  
          bbox = src.bbox_layer(bbox_x).permute(0, 2, 3, 1).contiguous().view(x.size(0), -1, 4)
          conf = src.conf_layer(conf_x).permute(0, 2, 3, 1).contiguous().view(x.size(0), -1, self.num_classes)
          
          if cfg.eval_mask_branch:
              mask = src.mask_layer(mask_x).permute(0, 2, 3, 1).contiguous().view(x.size(0), -1, self.mask_dim)
          else:
              mask = torch.zeros(x.size(0), bbox.size(1), self.mask_dim, device=bbox.device)
  
          if cfg.use_mask_scoring:
              score = src.score_layer(x).permute(0, 2, 3, 1).contiguous().view(x.size(0), -1, 1)
  
          if cfg.use_instance_coeff:
              inst = src.inst_layer(x).permute(0, 2, 3, 1).contiguous().view(x.size(0), -1, cfg.num_instance_coeffs)    
  
          # See box_utils.decode for an explanation of this
          if cfg.use_yolo_regressors:
              bbox[:, :, :2] = torch.sigmoid(bbox[:, :, :2]) - 0.5
              bbox[:, :, 0] /= conv_w
              bbox[:, :, 1] /= conv_h
  
          if cfg.eval_mask_branch:
              if cfg.mask_type == mask_type.direct:
                  mask = torch.sigmoid(mask)
              elif cfg.mask_type == mask_type.lincomb:
                  mask = cfg.mask_proto_coeff_activation(mask)
  
                  if cfg.mask_proto_coeff_gate:
                      gate = src.gate_layer(x).permute(0, 2, 3, 1).contiguous().view(x.size(0), -1, self.mask_dim)
                      mask = mask * torch.sigmoid(gate)
  
          if cfg.mask_proto_split_prototypes_by_head and cfg.mask_type == mask_type.lincomb:
              mask = F.pad(mask, (self.index * self.mask_dim, (self.num_heads - self.index - 1) * self.mask_dim), mode='constant', value=0)
          
          priors = self.make_priors(conv_h, conv_w, x.device)
  
          preds = { 'loc': bbox, 'conf': conf, 'mask': mask, 'priors': priors }
  
          if cfg.use_mask_scoring:
              preds['score'] = score
  
          if cfg.use_instance_coeff:
              preds['inst'] = inst
          
          return preds
  
      def make_priors(self, conv_h, conv_w, device):
          """ Note that priors are [x,y,width,height] where (x,y) is the center of the box. """
          global prior_cache
          size = (conv_h, conv_w)
  
          with timer.env('makepriors'):
              if self.last_img_size != (cfg._tmp_img_w, cfg._tmp_img_h):
                  prior_data = []
  
                  # Iteration order is important (it has to sync up with the convout)
                  for j, i in product(range(conv_h), range(conv_w)):
                      # +0.5 because priors are in center-size notation
                      x = (i + 0.5) / conv_w
                      y = (j + 0.5) / conv_h
                      
                      for ars in self.aspect_ratios:
                          for scale in self.scales:
                              for ar in ars:
                                  if not cfg.backbone.preapply_sqrt:
                                      ar = sqrt(ar)
  
                                  if cfg.backbone.use_pixel_scales:
                                      w = scale * ar / cfg.max_size
                                      h = scale / ar / cfg.max_size
                                  else:
                                      w = scale * ar / conv_w
                                      h = scale / ar / conv_h
                                  
                                  # This is for backward compatability with a bug where I made everything square by accident
                                  if cfg.backbone.use_square_anchors:
                                      h = w
  
                                  prior_data += [x, y, w, h]
  
                  self.priors = torch.Tensor(prior_data, device=device).view(-1, 4).detach()
                  self.priors.requires_grad = False
                  self.last_img_size = (cfg._tmp_img_w, cfg._tmp_img_h)
                  self.last_conv_size = (conv_w, conv_h)
                  prior_cache[size] = None
              elif self.priors.device != device:
                  # This whole weird situation is so that DataParalell doesn't copy the priors each iteration
                  if prior_cache[size] is None:
                      prior_cache[size] = {}
                  
                  if device not in prior_cache[size]:
                      prior_cache[size][device] = self.priors.to(device)
  
                  self.priors = prior_cache[size][device]
          
          return self.priors
  
  class FPN(ScriptModuleWrapper):
      """
      Implements a general version of the FPN introduced in
      https://arxiv.org/pdf/1612.03144.pdf
  
      Parameters (in cfg.fpn):
          - num_features (int): The number of output features in the fpn layers.
          - interpolation_mode (str): The mode to pass to F.interpolate.
          - num_downsample (int): The number of downsampled layers to add onto the selected layers.
                                  These extra layers are downsampled from the last selected layer.
  
      Args:
          - in_channels (list): For each conv layer you supply in the forward pass,
                                how many features will it have?
      """
      __constants__ = ['interpolation_mode', 'num_downsample', 'use_conv_downsample', 'relu_pred_layers',
                       'lat_layers', 'pred_layers', 'downsample_layers', 'relu_downsample_layers']
  
      def __init__(self, in_channels):
          super().__init__()
  
          self.lat_layers  = nn.ModuleList([
              nn.Conv2d(x, cfg.fpn.num_features, kernel_size=1)
              for x in reversed(in_channels)
          ])
  
          # This is here for backwards compatability
          padding = 1 if cfg.fpn.pad else 0
          self.pred_layers = nn.ModuleList([
              nn.Conv2d(cfg.fpn.num_features, cfg.fpn.num_features, kernel_size=3, padding=padding)
              for _ in in_channels
          ])
  
          if cfg.fpn.use_conv_downsample:
              self.downsample_layers = nn.ModuleList([
                  nn.Conv2d(cfg.fpn.num_features, cfg.fpn.num_features, kernel_size=3, padding=1, stride=2)
                  for _ in range(cfg.fpn.num_downsample)
              ])
          
          self.interpolation_mode     = cfg.fpn.interpolation_mode
          self.num_downsample         = cfg.fpn.num_downsample
          self.use_conv_downsample    = cfg.fpn.use_conv_downsample
          self.relu_downsample_layers = cfg.fpn.relu_downsample_layers
          self.relu_pred_layers       = cfg.fpn.relu_pred_layers
  
      @script_method_wrapper
      def forward(self, convouts:List[torch.Tensor]):
          """
          Args:
              - convouts (list): A list of convouts for the corresponding layers in in_channels.
          Returns:
              - A list of FPN convouts in the same order as x with extra downsample layers if requested.
          """
  
          out = []
          x = torch.zeros(1, device=convouts[0].device)
          for i in range(len(convouts)):
              out.append(x)
  
          # For backward compatability, the conv layers are stored in reverse but the input and output is
          # given in the correct order. Thus, use j=-i-1 for the input and output and i for the conv layers.
          j = len(convouts)
          for lat_layer in self.lat_layers:
              j -= 1
  
              if j < len(convouts) - 1:
                  _, _, h, w = convouts[j].size()
                  x = F.interpolate(x, size=(h, w), mode=self.interpolation_mode, align_corners=False)
              
              x = x + lat_layer(convouts[j])
              out[j] = x
          
          # This janky second loop is here because TorchScript.
          j = len(convouts)
          for pred_layer in self.pred_layers:
              j -= 1
              out[j] = pred_layer(out[j])
  
              if self.relu_pred_layers:
                  F.relu(out[j], inplace=True)
  
          cur_idx = len(out)
  
          # In the original paper, this takes care of P6
          if self.use_conv_downsample:
              for downsample_layer in self.downsample_layers:
                  out.append(downsample_layer(out[-1]))
          else:
              for idx in range(self.num_downsample):
                  # Note: this is an untested alternative to out.append(out[-1][:, :, ::2, ::2]). Thanks TorchScript.
                  out.append(nn.functional.max_pool2d(out[-1], 1, stride=2))
  
          if self.relu_downsample_layers:
              for idx in range(len(out) - cur_idx):
                  out[idx] = F.relu(out[idx + cur_idx], inplace=False)
  
          return out
  
  class FastMaskIoUNet(ScriptModuleWrapper):
  
      def __init__(self):
          super().__init__()
          input_channels = 1
          last_layer = [(cfg.num_classes-1, 1, {})]
          self.maskiou_net, _ = make_net(input_channels, cfg.maskiou_net + last_layer, include_last_relu=True)
  
      def forward(self, x):
          x = self.maskiou_net(x)
          maskiou_p = F.max_pool2d(x, kernel_size=x.size()[2:]).squeeze(-1).squeeze(-1)
  
          return maskiou_p
  
  
  
  class Yolact(nn.Module):
      """
  
  
      ██╗   ██╗ ██████╗ ██╗      █████╗  ██████╗████████╗
      ╚██╗ ██╔╝██╔═══██╗██║     ██╔══██╗██╔════╝╚══██╔══╝
       ╚████╔╝ ██║   ██║██║     ███████║██║        ██║   
        ╚██╔╝  ██║   ██║██║     ██╔══██║██║        ██║   
         ██║   ╚██████╔╝███████╗██║  ██║╚██████╗   ██║   
         ╚═╝    ╚═════╝ ╚══════╝╚═╝  ╚═╝ ╚═════╝   ╚═╝ 
  
  
      You can set the arguments by changing them in the backbone config object in config.py.
  
      Parameters (in cfg.backbone):
          - selected_layers: The indices of the conv layers to use for prediction.
          - pred_scales:     A list with len(selected_layers) containing tuples of scales (see PredictionModule)
          - pred_aspect_ratios: A list of lists of aspect ratios with len(selected_layers) (see PredictionModule)
      """
  
      def __init__(self, only_last_layer=False):
          super().__init__()
          
          self.only_last_layer = only_last_layer
          self.backbone = construct_backbone(cfg.backbone)
  
          if cfg.freeze_bn:
              self.freeze_bn()
  
          # Compute mask_dim here and add it back to the config. Make sure Yolact's constructor is called early!
          if cfg.mask_type == mask_type.direct:
              cfg.mask_dim = cfg.mask_size**2
          elif cfg.mask_type == mask_type.lincomb:
              if cfg.mask_proto_use_grid:
                  self.grid = torch.Tensor(np.load(cfg.mask_proto_grid_file))
                  self.num_grids = self.grid.size(0)
              else:
                  self.num_grids = 0
  
              self.proto_src = cfg.mask_proto_src
              
              if self.proto_src is None: in_channels = 3
              elif cfg.fpn is not None: in_channels = cfg.fpn.num_features
              else: in_channels = self.backbone.channels[self.proto_src]
              in_channels += self.num_grids
  
              # The include_last_relu=false here is because we might want to change it to another function
              self.proto_net, cfg.mask_dim = make_net(in_channels, cfg.mask_proto_net, include_last_relu=False)
  
              if cfg.mask_proto_bias:
                  cfg.mask_dim += 1
  
  
          self.selected_layers = cfg.backbone.selected_layers
          src_channels = self.backbone.channels
  
          if cfg.use_maskiou:
              self.maskiou_net = FastMaskIoUNet()
  
          if cfg.fpn is not None:
              # Some hacky rewiring to accomodate the FPN
              self.fpn = FPN([src_channels[i] for i in self.selected_layers])
              self.selected_layers = list(range(len(self.selected_layers) + cfg.fpn.num_downsample))
              src_channels = [cfg.fpn.num_features] * len(self.selected_layers)
  
  
          self.prediction_layers = nn.ModuleList()
          cfg.num_heads = len(self.selected_layers)
  
          for idx, layer_idx in enumerate(self.selected_layers):
              # If we're sharing prediction module weights, have every module's parent be the first one
              parent = None
              if cfg.share_prediction_module and idx > 0:
                  parent = self.prediction_layers[0]
  
              pred = PredictionModule(src_channels[layer_idx], src_channels[layer_idx],
                                      aspect_ratios = cfg.backbone.pred_aspect_ratios[idx],
                                      scales        = cfg.backbone.pred_scales[idx],
                                      parent        = parent,
                                      index         = idx)
              self.prediction_layers.append(pred)
  
          # Extra parameters for the extra losses
          if cfg.use_class_existence_loss:
              # This comes from the smallest layer selected
              # Also note that cfg.num_classes includes background
              self.class_existence_fc = nn.Linear(src_channels[-1], cfg.num_classes - 1)
          
          if cfg.use_semantic_segmentation_loss:
              self.semantic_seg_conv = nn.Conv2d(src_channels[0], cfg.num_classes-1, kernel_size=1)
  
          # For use in evaluation
          self.detect = Detect(cfg.num_classes, bkg_label=0, top_k=cfg.nms_top_k,
              conf_thresh=cfg.nms_conf_thresh, nms_thresh=cfg.nms_thresh)
  
      def save_weights(self, path):
          """ Saves the model's weights using compression because the file sizes were getting too big. """
          torch.save(self.state_dict(), path)
      
      def load_weights(self, path):
          """ Loads weights from a compressed save file. """
          state_dict = torch.load(path)
  
          # For backward compatability, remove these (the new variable is called layers)
          for key in list(state_dict.keys()):
              if key.startswith('backbone.layer') and not key.startswith('backbone.layers'):
                  del state_dict[key]
          
              # Also for backward compatibility with v1.0 weights, do this check
              if key.startswith('fpn.downsample_layers.'):
                  if cfg.fpn is not None and int(key.split('.')[2]) >= cfg.fpn.num_downsample:
                      del state_dict[key]
          # Uncomment this in normal conditions
          # self.load_state_dict(state_dict)
          # Added this for fine-tuning. Comment this in normal conditions.
          try:
              self.load_state_dict(state_dict)
          except RuntimeError as e:
              print('Ignoring "' + str(e) + '"')
  
      def init_weights(self, backbone_path):
          """ Initialize weights for training. """
          # Initialize the backbone with the pretrained weights.
          self.backbone.init_backbone(backbone_path)
  
          conv_constants = getattr(nn.Conv2d(1, 1, 1), '__constants__')
          
          # Quick lambda to test if one list contains the other
          def all_in(x, y):
              for _x in x:
                  if _x not in y:
                      return False
              return True
  
          # Initialize the rest of the conv layers with xavier
          for name, module in self.named_modules():
              # See issue #127 for why we need such a complicated condition if the module is a WeakScriptModuleProxy
              # Broke in 1.3 (see issue #175), WeakScriptModuleProxy was turned into just ScriptModule.
              # Broke in 1.4 (see issue #292), where RecursiveScriptModule is the new star of the show.
              # Note that this might break with future pytorch updates, so let me know if it does
              is_script_conv = False
              if 'Script' in type(module).__name__:
                  # 1.4 workaround: now there's an original_name member so just use that
                  if hasattr(module, 'original_name'):
                      is_script_conv = 'Conv' in module.original_name
                  # 1.3 workaround: check if this has the same constants as a conv module
                  else:
                      is_script_conv = (
                          all_in(module.__dict__['_constants_set'], conv_constants)
                          and all_in(conv_constants, module.__dict__['_constants_set']))
              
              is_conv_layer = isinstance(module, nn.Conv2d) or is_script_conv
  
              if is_conv_layer and module not in self.backbone.backbone_modules:
                  nn.init.xavier_uniform_(module.weight.data)
  
                  if module.bias is not None:
                      if cfg.use_focal_loss and 'conf_layer' in name:
                          if not cfg.use_sigmoid_focal_loss:
                              # Initialize the last layer as in the focal loss paper.
                              # Because we use softmax and not sigmoid, I had to derive an alternate expression
                              # on a notecard. Define pi to be the probability of outputting a foreground detection.
                              # Then let z = sum(exp(x)) - exp(x_0). Finally let c be the number of foreground classes.
                              # Chugging through the math, this gives us
                              #   x_0 = log(z * (1 - pi) / pi)    where 0 is the background class
                              #   x_i = log(z / c)                for all i > 0
                              # For simplicity (and because we have a degree of freedom here), set z = 1. Then we have
                              #   x_0 =  log((1 - pi) / pi)       note: don't split up the log for numerical stability
                              #   x_i = -log(c)                   for all i > 0
                              module.bias.data[0]  = np.log((1 - cfg.focal_loss_init_pi) / cfg.focal_loss_init_pi)
                              module.bias.data[1:] = -np.log(module.bias.size(0) - 1)
                          else:
                              module.bias.data[0]  = -np.log(cfg.focal_loss_init_pi / (1 - cfg.focal_loss_init_pi))
                              module.bias.data[1:] = -np.log((1 - cfg.focal_loss_init_pi) / cfg.focal_loss_init_pi)
                      else:
                          module.bias.data.zero_()
      
      def train(self, mode=True):
          super().train(mode)
  
          if cfg.freeze_bn:
              self.freeze_bn()
  
      def freeze_bn(self, enable=False):
          """ Adapted from https://discuss.pytorch.org/t/how-to-train-with-frozen-batchnorm/12106/8 """
          for module in self.modules():
              if isinstance(module, nn.BatchNorm2d):
                  module.train() if enable else module.eval()
  
                  module.weight.requires_grad = enable
                  module.bias.requires_grad = enable
      
      def forward(self, x):
          """ The input should be of size [batch_size, 3, img_h, img_w] """
          _, _, img_h, img_w = x.size()
          cfg._tmp_img_h = img_h
          cfg._tmp_img_w = img_w
          
          with timer.env('backbone'):
              outs = self.backbone(x)
  
          if cfg.fpn is not None:
              with timer.env('fpn'):
                  # Use backbone.selected_layers because we overwrote self.selected_layers
                  outs = [outs[i] for i in cfg.backbone.selected_layers]
                  outs = self.fpn(outs)
  
          proto_out = None
          if cfg.mask_type == mask_type.lincomb and cfg.eval_mask_branch:
              with timer.env('proto'):
                  proto_x = x if self.proto_src is None else outs[self.proto_src]
                  
                  if self.num_grids > 0:
                      grids = self.grid.repeat(proto_x.size(0), 1, 1, 1)
                      proto_x = torch.cat([proto_x, grids], dim=1)
  
                  proto_out = self.proto_net(proto_x)
                  proto_out = cfg.mask_proto_prototype_activation(proto_out)
  
                  if cfg.mask_proto_prototypes_as_features:
                      # Clone here because we don't want to permute this, though idk if contiguous makes this unnecessary
                      proto_downsampled = proto_out.clone()
  
                      if cfg.mask_proto_prototypes_as_features_no_grad:
                          proto_downsampled = proto_out.detach()
                  
                  # Move the features last so the multiplication is easy
                  proto_out = proto_out.permute(0, 2, 3, 1).contiguous()
  
                  if cfg.mask_proto_bias:
                      bias_shape = [x for x in proto_out.size()]
                      bias_shape[-1] = 1
                      proto_out = torch.cat([proto_out, torch.ones(*bias_shape)], -1)
  
  
          with timer.env('pred_heads'):
              pred_outs = { 'loc': [], 'conf': [], 'mask': [], 'priors': [] }
  
              if cfg.use_mask_scoring:
                  pred_outs['score'] = []
  
              if cfg.use_instance_coeff:
                  pred_outs['inst'] = []
              
              for idx, pred_layer in zip(self.selected_layers, self.prediction_layers):
                  pred_x = outs[idx]
  
                  if cfg.mask_type == mask_type.lincomb and cfg.mask_proto_prototypes_as_features:
                      # Scale the prototypes down to the current prediction layer's size and add it as inputs
                      proto_downsampled = F.interpolate(proto_downsampled, size=outs[idx].size()[2:], mode='bilinear', align_corners=False)
                      pred_x = torch.cat([pred_x, proto_downsampled], dim=1)
  
                  # A hack for the way dataparallel works
                  if cfg.share_prediction_module and pred_layer is not self.prediction_layers[0]:
                      pred_layer.parent = [self.prediction_layers[0]]
                  
                  if self.only_last_layer:
                      p = pred_layer(pred_x.detach())
                  else:
                      p = pred_layer(pred_x)
                  
                  for k, v in p.items():
                      pred_outs[k].append(v)
  
          for k, v in pred_outs.items():
              pred_outs[k] = torch.cat(v, -2)
  
          if proto_out is not None:
              pred_outs['proto'] = proto_out
  
          if self.training:
              # For the extra loss functions
              if cfg.use_class_existence_loss:
                  pred_outs['classes'] = self.class_existence_fc(outs[-1].mean(dim=(2, 3)))
  
              if cfg.use_semantic_segmentation_loss:
                  pred_outs['segm'] = self.semantic_seg_conv(outs[0])
  
              return pred_outs
          else:
              if cfg.use_mask_scoring:
                  pred_outs['score'] = torch.sigmoid(pred_outs['score'])
  
              if cfg.use_focal_loss:
                  if cfg.use_sigmoid_focal_loss:
                      # Note: even though conf[0] exists, this mode doesn't train it so don't use it
                      pred_outs['conf'] = torch.sigmoid(pred_outs['conf'])
                      if cfg.use_mask_scoring:
                          pred_outs['conf'] *= pred_outs['score']
                  elif cfg.use_objectness_score:
                      # See focal_loss_sigmoid in multibox_loss.py for details
                      objectness = torch.sigmoid(pred_outs['conf'][:, :, 0])
                      pred_outs['conf'][:, :, 1:] = objectness[:, :, None] * F.softmax(pred_outs['conf'][:, :, 1:], -1)
                      pred_outs['conf'][:, :, 0 ] = 1 - objectness
                  else:
                      pred_outs['conf'] = F.softmax(pred_outs['conf'], -1)
              else:
  
                  if cfg.use_objectness_score:
                      objectness = torch.sigmoid(pred_outs['conf'][:, :, 0])
                      
                      pred_outs['conf'][:, :, 1:] = (objectness > 0.10)[..., None] \
                          * F.softmax(pred_outs['conf'][:, :, 1:], dim=-1)
                      
                  else:
                      pred_outs['conf'] = F.softmax(pred_outs['conf'], -1)
  
              return self.detect(pred_outs, self)
  
  
  
  
  # Some testing code
  if __name__ == '__main__':
      from utils.functions import init_console
      init_console()
  
      # Use the first argument to set the config if you want
      import sys
      if len(sys.argv) > 1:
          from data.config import set_cfg
          set_cfg(sys.argv[1])
  
      net = Yolact()
      net.train()
      net.init_weights(backbone_path='weights/' + cfg.backbone.path)
  
      # GPU
      net = net.cuda()
      torch.set_default_tensor_type('torch.cuda.FloatTensor')
  
      x = torch.zeros((1, 3, cfg.max_size, cfg.max_size))
      y = net(x)
  
      for p in net.prediction_layers:
          print(p.last_conv_size)
  
      print()
      for k, a in y.items():
          print(k + ': ', a.size(), torch.sum(a))
      exit()
      
      net(x)
      # timer.disable('pass2')
      avg = MovingAverage()
      try:
          while True:
              timer.reset()
              with timer.env('everything else'):
                  net(x)
              avg.add(timer.total_time())
              print('\033[2J') # Moves console cursor to 0,0
              timer.print_stats()
              print('Avg fps: %.2f\tAvg ms: %.2f         ' % (1/avg.get_avg(), avg.get_avg()*1000))
      except KeyboardInterrupt:
          pass
  
apis: torch.nn.init.xavier_uniform_ torch.nn.functional.softmax torch.set_default_tensor_type numpy.log torch.nn.ModuleList torch.nn.Conv2d torch.cat torch.nn.BatchNorm2d torch.nn.functional.pad torch.cuda.device_count torch.sigmoid torch.Tensor numpy.load torch.ones torch.load torch.nn.functional.max_pool2d torch.cuda.current_device torch.sum torch.nn.Linear torch.nn.functional.relu torch.zeros torch.nn.ReLU torch.nn.functional.interpolate