code: def forward(self, feats, pad_mask=None, gt_meta=None):
      feat0 = feats.pop(0)
      # input projection and embedding
      (
          feat_flatten,
          spatial_shapes,
          level_start_index,
          mask_flatten,
          lvl_pos_embed_flatten,
          valid_ratios,
      ) = self._get_encoder_input(feats, pad_mask)
  
      # encoder
      memory = self.encoder(
          feat_flatten,
          spatial_shapes,
          level_start_index,
          mask_flatten,
          lvl_pos_embed_flatten,
          valid_ratios,
      )
  
      mask_feat = self._get_encoder_mask_feature(
          feat0, memory, spatial_shapes
      )
  
      # prepare denoising training
      if self.training:
          (
              denoising_class,
              denoising_bbox_unact,
              attn_mask,
              dn_meta,
          ) = get_denoising_training_group(
              gt_meta,
              self.num_classes,
              self.num_queries,
              self.denoising_class_embed.weight,
              self.num_denoising,
              self.label_noise_ratio,
              self.box_noise_scale,
          )
      else:
          denoising_class, denoising_bbox_unact, attn_mask, dn_meta = (
              None,
              None,
              None,
              None,
          )
  
      (
          target,
          init_ref_points_unact,
          enc_out,
          init_out,
      ) = self._get_decoder_input(
          memory,
          mask_feat,
          spatial_shapes,
          mask_flatten,
          denoising_class,
          denoising_bbox_unact,
      )
  
      # decoder
      inter_feats, inter_bboxes = self.decoder(
          target,
          init_ref_points_unact,
          memory,
          spatial_shapes,
          level_start_index,
          self.bbox_head,
          self.query_pos_head,
          self.dec_norm,
          valid_ratios,
          attn_mask,
          mask_flatten,
      )
  
      out_logits = []
      out_bboxes = []
      out_masks = []
      for i in range(self.num_decoder_layers):
          if self.training or i == self.num_decoder_layers - 1:
              logits_, masks_ = self._get_pred_class_and_mask(
                  inter_feats[i], mask_feat
              )
          else:
              continue
          out_logits.append(logits_)
          out_masks.append(masks_)
          if i == 0:
              out_bboxes.append(
                  F.sigmoid(
                      self.bbox_head(inter_feats[i])
                      + init_ref_points_unact
                  )
              )
          else:
              out_bboxes.append(
                  F.sigmoid(
                      self.bbox_head(inter_feats[i])
                      + inverse_sigmoid(inter_bboxes[i - 1])
                  )
              )
      out_bboxes = paddle.stack(out_bboxes)
      out_logits = paddle.stack(out_logits)
      out_masks = paddle.stack(out_masks)
  
      return (
          out_logits,
          out_bboxes,
          out_masks,
          enc_out,
          init_out,
          dn_meta,
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import math
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddle import ParamAttr
  from paddle.regularizer import L2Decay
  from ppdet.core.workspace import register
  from .position_encoding import PositionEmbedding
  from ..heads.detr_head import MLP
  from .deformable_transformer import DeformableTransformerEncoderLayer, DeformableTransformerEncoder
  from .dino_transformer import DINOTransformerDecoderLayer
  from ..initializer import linear_init_, constant_, xavier_uniform_, bias_init_with_prob
  from .utils import _get_clones, get_valid_ratio, get_denoising_training_group, get_sine_pos_embed, inverse_sigmoid, mask_to_box_coordinate
label_desc: Use image node_id 6 for calling the MaskDINO obj's underlying member method code with example usage: obj.forward(feats, pad_mask, gt_meta) and returns: out_logits,  out_bboxes,  out_masks,  enc_out,  init_out,  dn_meta