code: def forward(self, x, mask=None, attn_mask=None):
      for attn, ff in self.layers:
          x = attn(x, mask=mask, attn_mask=attn_mask) + x
          x = ff(x) + x
  
      return self.norm(x)
  
imports: from functools import partial
  from typing import List, Union
  import torch
  import torch.nn.functional
  from torch import nn, Tensor
  from torch.nn.utils.rnn import pad_sequence
  from einops import rearrange, repeat
  from einops.layers.torch import Rearrange
label_desc: Use image node_id 2 for calling the Transformer obj's underlying member method code with example usage: obj.forward(x, mask, attn_mask) and returns: self