code: def forward(
      self,
      tgt,
      reference_points,
      memory,
      memory_spatial_shapes,
      memory_level_start_index,
      memory_mask=None,
      query_pos_embed=None,
  ):
      # self attention
      q = k = self.with_pos_embed(tgt, query_pos_embed)
      tgt2 = self.self_attn(q, k, value=tgt)
      tgt = tgt + self.dropout1(tgt2)
      tgt = self.norm1(tgt)
  
      # cross attention
      tgt2 = self.cross_attn(
          self.with_pos_embed(tgt, query_pos_embed),
          reference_points,
          memory,
          memory_spatial_shapes,
          memory_level_start_index,
          memory_mask,
      )
      tgt = tgt + self.dropout2(tgt2)
      tgt = self.norm2(tgt)
  
      # ffn
      tgt = self.forward_ffn(tgt)
  
      return tgt
  
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 ppdet.core.workspace import register
  from ..layers import MultiHeadAttention
  from .position_encoding import PositionEmbedding
  from .utils import _get_clones, get_valid_ratio
  from ..initializer import linear_init_, constant_, xavier_uniform_, normal_
label_desc: Use image node_id 5 for calling the DeformableTransformerDecoderLayer obj's underlying member method code with example usage: obj.forward(tgt, reference_points, memory, memory_spatial_shapes, memory_level_start_index, memory_mask, query_pos_embed) and returns: tgt