code: def forward(
      self,
      feat,
      spatial_shapes,
      level_start_index,
      feat_mask=None,
      query_pos_embed=None,
      valid_ratios=None,
  ):
      if valid_ratios is None:
          valid_ratios = paddle.ones(
              [feat.shape[0], spatial_shapes.shape[0], 2]
          )
      reference_points = self.get_reference_points(
          spatial_shapes, valid_ratios
      )
      for layer in self.layers:
          feat = layer(
              feat,
              reference_points,
              spatial_shapes,
              level_start_index,
              feat_mask,
              query_pos_embed,
          )
  
      return feat
  
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 3 for calling the DeformableTransformerEncoder obj's underlying member method code with example usage: obj.forward(feat, spatial_shapes, level_start_index, feat_mask, query_pos_embed, valid_ratios) and returns: feat