text: """ Visformer
  
  Paper: Visformer: The Vision-friendly Transformer - https://arxiv.org/abs/2104.12533
  
  From original at https://github.com/danczs/Visformer
  
  """
  from copy import deepcopy
  
  import torch
  import torch.nn as nn
  import torch.nn.functional as F
  
  from timm.data import IMAGENET_DEFAULT_MEAN, IMAGENET_DEFAULT_STD
  from .helpers import build_model_with_cfg, overlay_external_default_cfg
  from .layers import to_2tuple, trunc_normal_, DropPath, PatchEmbed, LayerNorm2d, create_classifier
  from .registry import register_model
  
  
  __all__ = ['Visformer']
  
  
  def _cfg(url='', **kwargs):
      return {
          'url': url,
          'num_classes': 1000, 'input_size': (3, 224, 224), 'pool_size': None,
          'crop_pct': .9, 'interpolation': 'bicubic', 'fixed_input_size': True,
          'mean': IMAGENET_DEFAULT_MEAN, 'std': IMAGENET_DEFAULT_STD,
          'first_conv': 'stem.0', 'classifier': 'head',
          **kwargs
      }
  
  
  default_cfgs = dict(
      visformer_tiny=_cfg(),
      visformer_small=_cfg(
          url='https://github.com/rwightman/pytorch-image-models/releases/download/v0.1-vt3p-weights/visformer_small-839e1f5b.pth'
      ),
  )
  
  
  class SpatialMlp(nn.Module):
      def __init__(self, in_features, hidden_features=None, out_features=None,
                   act_layer=nn.GELU, drop=0., group=8, spatial_conv=False):
          super().__init__()
          out_features = out_features or in_features
          hidden_features = hidden_features or in_features
          self.in_features = in_features
          self.out_features = out_features
          self.spatial_conv = spatial_conv
          if self.spatial_conv:
              if group < 2:  # net setting
                  hidden_features = in_features * 5 // 6
              else:
                  hidden_features = in_features * 2
          self.hidden_features = hidden_features
          self.group = group
          self.drop = nn.Dropout(drop)
          self.conv1 = nn.Conv2d(in_features, hidden_features, 1, stride=1, padding=0, bias=False)
          self.act1 = act_layer()
          if self.spatial_conv:
              self.conv2 = nn.Conv2d(
                  hidden_features, hidden_features, 3, stride=1, padding=1, groups=self.group, bias=False)
              self.act2 = act_layer()
          else:
              self.conv2 = None
              self.act2 = None
          self.conv3 = nn.Conv2d(hidden_features, out_features, 1, stride=1, padding=0, bias=False)
  
      def forward(self, x):
          x = self.conv1(x)
          x = self.act1(x)
          x = self.drop(x)
          if self.conv2 is not None:
              x = self.conv2(x)
              x = self.act2(x)
          x = self.conv3(x)
          x = self.drop(x)
          return x
  
  
  class Attention(nn.Module):
      def __init__(self, dim, num_heads=8, head_dim_ratio=1., attn_drop=0., proj_drop=0.):
          super().__init__()
          self.dim = dim
          self.num_heads = num_heads
          head_dim = round(dim // num_heads * head_dim_ratio)
          self.head_dim = head_dim
          self.scale = head_dim ** -0.5
          self.qkv = nn.Conv2d(dim, head_dim * num_heads * 3, 1, stride=1, padding=0, bias=False)
          self.attn_drop = nn.Dropout(attn_drop)
          self.proj = nn.Conv2d(self.head_dim * self.num_heads, dim, 1, stride=1, padding=0, bias=False)
          self.proj_drop = nn.Dropout(proj_drop)
  
      def forward(self, x):
          B, C, H, W = x.shape
          x = self.qkv(x).reshape(B, 3, self.num_heads, self.head_dim, -1).permute(1, 0, 2, 4, 3)
          q, k, v = x[0], x[1], x[2]
  
          attn = (q @ k.transpose(-2, -1)) * self.scale
          attn = attn.softmax(dim=-1)
          attn = self.attn_drop(attn)
          x = attn @ v
  
          x = x.permute(0, 1, 3, 2).reshape(B, -1, H, W)
          x = self.proj(x)
          x = self.proj_drop(x)
          return x
  
  
  class Block(nn.Module):
      def __init__(self, dim, num_heads, head_dim_ratio=1., mlp_ratio=4.,
                   drop=0., attn_drop=0., drop_path=0., act_layer=nn.GELU, norm_layer=LayerNorm2d,
                   group=8, attn_disabled=False, spatial_conv=False):
          super().__init__()
          self.spatial_conv = spatial_conv
          self.drop_path = DropPath(drop_path) if drop_path > 0. else nn.Identity()
          if attn_disabled:
              self.norm1 = None
              self.attn = None
          else:
              self.norm1 = norm_layer(dim)
              self.attn = Attention(
                  dim, num_heads=num_heads, head_dim_ratio=head_dim_ratio, attn_drop=attn_drop, proj_drop=drop)
  
          self.norm2 = norm_layer(dim)
          mlp_hidden_dim = int(dim * mlp_ratio)
          self.mlp = SpatialMlp(
              in_features=dim, hidden_features=mlp_hidden_dim, act_layer=act_layer, drop=drop,
              group=group, spatial_conv=spatial_conv)  # new setting
  
      def forward(self, x):
          if self.attn is not None:
              x = x + self.drop_path(self.attn(self.norm1(x)))
          x = x + self.drop_path(self.mlp(self.norm2(x)))
          return x
  
  
  class Visformer(nn.Module):
      def __init__(self, img_size=224, patch_size=16, in_chans=3, num_classes=1000, init_channels=32, embed_dim=384,
                   depth=12, num_heads=6, mlp_ratio=4., drop_rate=0., attn_drop_rate=0., drop_path_rate=0.,
                   norm_layer=LayerNorm2d, attn_stage='111', pos_embed=True, spatial_conv='111',
                   vit_stem=False, group=8, global_pool='avg', conv_init=False, embed_norm=None):
          super().__init__()
          img_size = to_2tuple(img_size)
          self.num_classes = num_classes
          self.embed_dim = embed_dim
          self.init_channels = init_channels
          self.img_size = img_size
          self.vit_stem = vit_stem
          self.conv_init = conv_init
          if isinstance(depth, (list, tuple)):
              self.stage_num1, self.stage_num2, self.stage_num3 = depth
              depth = sum(depth)
          else:
              self.stage_num1 = self.stage_num3 = depth // 3
              self.stage_num2 = depth - self.stage_num1 - self.stage_num3
          self.pos_embed = pos_embed
          dpr = [x.item() for x in torch.linspace(0, drop_path_rate, depth)]
  
          # stage 1
          if self.vit_stem:
              self.stem = None
              self.patch_embed1 = PatchEmbed(
                  img_size=img_size, patch_size=patch_size, in_chans=in_chans,
                  embed_dim=embed_dim, norm_layer=embed_norm, flatten=False)
              img_size = [x // 16 for x in img_size]
          else:
              if self.init_channels is None:
                  self.stem = None
                  self.patch_embed1 = PatchEmbed(
                      img_size=img_size, patch_size=patch_size // 2, in_chans=in_chans,
                      embed_dim=embed_dim // 2, norm_layer=embed_norm, flatten=False)
                  img_size = [x // 8 for x in img_size]
              else:
                  self.stem = nn.Sequential(
                      nn.Conv2d(in_chans, self.init_channels, 7, stride=2, padding=3, bias=False),
                      nn.BatchNorm2d(self.init_channels),
                      nn.ReLU(inplace=True)
                  )
                  img_size = [x // 2 for x in img_size]
                  self.patch_embed1 = PatchEmbed(
                      img_size=img_size, patch_size=patch_size // 4, in_chans=self.init_channels,
                      embed_dim=embed_dim // 2, norm_layer=embed_norm, flatten=False)
                  img_size = [x // 4 for x in img_size]
  
          if self.pos_embed:
              if self.vit_stem:
                  self.pos_embed1 = nn.Parameter(torch.zeros(1, embed_dim, *img_size))
              else:
                  self.pos_embed1 = nn.Parameter(torch.zeros(1, embed_dim//2, *img_size))
              self.pos_drop = nn.Dropout(p=drop_rate)
          self.stage1 = nn.ModuleList([
              Block(
                  dim=embed_dim//2, num_heads=num_heads, head_dim_ratio=0.5, mlp_ratio=mlp_ratio,
                  drop=drop_rate, attn_drop=attn_drop_rate, drop_path=dpr[i], norm_layer=norm_layer,
                  group=group, attn_disabled=(attn_stage[0] == '0'), spatial_conv=(spatial_conv[0] == '1')
              )
              for i in range(self.stage_num1)
          ])
  
          # stage2
          if not self.vit_stem:
              self.patch_embed2 = PatchEmbed(
                  img_size=img_size, patch_size=patch_size // 8, in_chans=embed_dim // 2,
                  embed_dim=embed_dim, norm_layer=embed_norm, flatten=False)
              img_size = [x // 2 for x in img_size]
              if self.pos_embed:
                  self.pos_embed2 = nn.Parameter(torch.zeros(1, embed_dim, *img_size))
          self.stage2 = nn.ModuleList([
              Block(
                  dim=embed_dim, num_heads=num_heads, head_dim_ratio=1.0, mlp_ratio=mlp_ratio,
                  drop=drop_rate, attn_drop=attn_drop_rate, drop_path=dpr[i], norm_layer=norm_layer,
                  group=group, attn_disabled=(attn_stage[1] == '0'), spatial_conv=(spatial_conv[1] == '1')
              )
              for i in range(self.stage_num1, self.stage_num1+self.stage_num2)
          ])
  
          # stage 3
          if not self.vit_stem:
              self.patch_embed3 = PatchEmbed(
                  img_size=img_size, patch_size=patch_size // 8, in_chans=embed_dim,
                  embed_dim=embed_dim * 2, norm_layer=embed_norm, flatten=False)
              img_size = [x // 2 for x in img_size]
              if self.pos_embed:
                  self.pos_embed3 = nn.Parameter(torch.zeros(1, embed_dim*2, *img_size))
          self.stage3 = nn.ModuleList([
              Block(
                  dim=embed_dim*2, num_heads=num_heads, head_dim_ratio=1.0, mlp_ratio=mlp_ratio,
                  drop=drop_rate, attn_drop=attn_drop_rate, drop_path=dpr[i], norm_layer=norm_layer,
                  group=group, attn_disabled=(attn_stage[2] == '0'), spatial_conv=(spatial_conv[2] == '1')
              )
              for i in range(self.stage_num1+self.stage_num2, depth)
          ])
  
          # head
          self.num_features = embed_dim if self.vit_stem else embed_dim * 2
          self.norm = norm_layer(self.num_features)
          self.global_pool, self.head = create_classifier(self.num_features, self.num_classes, pool_type=global_pool)
  
          # weights init
          if self.pos_embed:
              trunc_normal_(self.pos_embed1, std=0.02)
              if not self.vit_stem:
                  trunc_normal_(self.pos_embed2, std=0.02)
                  trunc_normal_(self.pos_embed3, std=0.02)
          self.apply(self._init_weights)
  
      def _init_weights(self, m):
          if isinstance(m, nn.Linear):
              trunc_normal_(m.weight, std=0.02)
              if m.bias is not None:
                  nn.init.constant_(m.bias, 0)
          elif isinstance(m, nn.LayerNorm):
              nn.init.constant_(m.bias, 0)
              nn.init.constant_(m.weight, 1.0)
          elif isinstance(m, nn.BatchNorm2d):
              nn.init.constant_(m.bias, 0)
              nn.init.constant_(m.weight, 1.0)
          elif isinstance(m, nn.Conv2d):
              if self.conv_init:
                  nn.init.kaiming_normal_(m.weight, mode='fan_out', nonlinearity='relu')
              else:
                  trunc_normal_(m.weight, std=0.02)
              if m.bias is not None:
                  nn.init.constant_(m.bias, 0.)
  
      def get_classifier(self):
          return self.head
  
      def reset_classifier(self, num_classes, global_pool='avg'):
          self.num_classes = num_classes
          self.global_pool, self.head = create_classifier(self.num_features, self.num_classes, pool_type=global_pool)
  
      def forward_features(self, x):
          if self.stem is not None:
              x = self.stem(x)
  
          # stage 1
          x = self.patch_embed1(x)
          if self.pos_embed:
              x = x + self.pos_embed1
              x = self.pos_drop(x)
          for b in self.stage1:
              x = b(x)
  
          # stage 2
          if not self.vit_stem:
              x = self.patch_embed2(x)
              if self.pos_embed:
                  x = x + self.pos_embed2
                  x = self.pos_drop(x)
          for b in self.stage2:
              x = b(x)
  
          # stage3
          if not self.vit_stem:
              x = self.patch_embed3(x)
              if self.pos_embed:
                  x = x + self.pos_embed3
                  x = self.pos_drop(x)
          for b in self.stage3:
              x = b(x)
  
          x = self.norm(x)
          return x
  
      def forward(self, x):
          x = self.forward_features(x)
          x = self.global_pool(x)
          x = self.head(x)
          return x
  
  
  def _create_visformer(variant, pretrained=False, default_cfg=None, **kwargs):
      if kwargs.get('features_only', None):
          raise RuntimeError('features_only not implemented for Vision Transformer models.')
      model = build_model_with_cfg(
          Visformer, variant, pretrained,
          default_cfg=default_cfgs[variant],
          **kwargs)
      return model
  
  
  @register_model
  def visformer_tiny(pretrained=False, **kwargs):
      model_cfg = dict(
          init_channels=16, embed_dim=192, depth=(7, 4, 4), num_heads=3, mlp_ratio=4., group=8,
          attn_stage='011', spatial_conv='100', norm_layer=nn.BatchNorm2d, conv_init=True,
          embed_norm=nn.BatchNorm2d, **kwargs)
      model = _create_visformer('visformer_tiny', pretrained=pretrained, **model_cfg)
      return model
  
  
  @register_model
  def visformer_small(pretrained=False, **kwargs):
      model_cfg = dict(
          init_channels=32, embed_dim=384, depth=(7, 4, 4), num_heads=6, mlp_ratio=4., group=8,
          attn_stage='011', spatial_conv='100', norm_layer=nn.BatchNorm2d, conv_init=True,
          embed_norm=nn.BatchNorm2d, **kwargs)
      model = _create_visformer('visformer_small', pretrained=pretrained, **model_cfg)
      return model
  
  
  # @register_model
  # def visformer_net1(pretrained=False, **kwargs):
  #     model = Visformer(
  #         init_channels=None, embed_dim=384, depth=(0, 12, 0), num_heads=6, mlp_ratio=4., attn_stage='111',
  #         spatial_conv='000', vit_stem=True, conv_init=True, **kwargs)
  #     model.default_cfg = _cfg()
  #     return model
  #
  #
  # @register_model
  # def visformer_net2(pretrained=False, **kwargs):
  #     model = Visformer(
  #         init_channels=32, embed_dim=384, depth=(0, 12, 0), num_heads=6, mlp_ratio=4., attn_stage='111',
  #         spatial_conv='000', vit_stem=False, conv_init=True, **kwargs)
  #     model.default_cfg = _cfg()
  #     return model
  #
  #
  # @register_model
  # def visformer_net3(pretrained=False, **kwargs):
  #     model = Visformer(
  #         init_channels=32, embed_dim=384, depth=12, num_heads=6, mlp_ratio=4., attn_stage='111',
  #         spatial_conv='000', vit_stem=False, conv_init=True, **kwargs)
  #     model.default_cfg = _cfg()
  #     return model
  #
  #
  # @register_model
  # def visformer_net4(pretrained=False, **kwargs):
  #     model = Visformer(
  #         init_channels=32, embed_dim=384, depth=12, num_heads=6, mlp_ratio=4., attn_stage='111',
  #         spatial_conv='000', vit_stem=False, conv_init=True, **kwargs)
  #     model.default_cfg = _cfg()
  #     return model
  #
  #
  # @register_model
  # def visformer_net5(pretrained=False, **kwargs):
  #     model = Visformer(
  #         init_channels=32, embed_dim=384, depth=12, num_heads=6, mlp_ratio=4., group=1, attn_stage='111',
  #         spatial_conv='111', vit_stem=False, conv_init=True, **kwargs)
  #     model.default_cfg = _cfg()
  #     return model
  #
  #
  # @register_model
  # def visformer_net6(pretrained=False, **kwargs):
  #     model = Visformer(
  #         init_channels=32, embed_dim=384, depth=12, num_heads=6, mlp_ratio=4., group=1, attn_stage='111',
  #         pos_embed=False, spatial_conv='111', conv_init=True, **kwargs)
  #     model.default_cfg = _cfg()
  #     return model
  #
  #
  # @register_model
  # def visformer_net7(pretrained=False, **kwargs):
  #     model = Visformer(
  #         init_channels=32, embed_dim=384, depth=(6, 7, 7), num_heads=6, group=1, attn_stage='000',
  #         pos_embed=False, spatial_conv='111', conv_init=True, **kwargs)
  #     model.default_cfg = _cfg()
  #     return model
  
  
  
  
  