code: def forward_ffn(self, src):
      src2 = self.linear2(
          self.dropout2(self.activation(self.linear1(src)))
      )
      src = src + self.dropout3(src2)
      src = self.norm2(src)
      return src
  
imports: import copy
  import numpy
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddleseg.cvlibs import param_init
  from paddlepanseg.models.param_init import c2_xavier_fill, THLinearInitMixin
  from .common import Conv2D, PositionEmbeddingSine
  from ._ms_deform_attn import MSDeformAttn
label_desc: Use image node_id 3 for calling the MSDeformAttnTransformerEncoderLayer obj's underlying member method code with example usage: obj.forward_ffn(src) and returns: src