class_docstr: The specific DWConv unsed in ConvFFN. 
code: def forward(self, x, H, W):
      B, N, C = x.shape
      n = N // 21
      x1 = (
          x[:, 0 : 16 * n, :]
          .transpose([0, 2, 1])
          .reshape([B, C, H * 2, W * 2])
      )
      x2 = (
          x[:, 16 * n : 20 * n, :]
          .transpose([0, 2, 1])
          .reshape([B, C, H, W])
      )
      x3 = (
          x[:, 20 * n :, :]
          .transpose([0, 2, 1])
          .reshape([B, C, H // 2, W // 2])
      )
      x1 = self.dwconv(x1).flatten(2).transpose([0, 2, 1])
      x2 = self.dwconv(x2).flatten(2).transpose([0, 2, 1])
      x3 = self.dwconv(x3).flatten(2).transpose([0, 2, 1])
      x = paddle.concat([x1, x2, x3], axis=1)
      return x
  
imports: import math
  import warnings
  from functools import partial
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddleseg.models.backbones.transformer_utils import DropPath
  from paddleseg.models.layers.ms_deformable_attention import MSDeformAttn
label_desc: Use image node_id 2 for calling the DWConv obj's underlying member method code with example usage: obj.forward(x, H, W) and returns: x