class_docstr: A transformer block, based on: "Dosovitskiy et al.,
  An Image is Worth 16x16 Words: Transformers for Image Recognition at Scale <https://arxiv.org/abs/2010.11929>"
code: def forward(self, x):
      x = x + self.attn(self.norm1(x))
      x = x + self.mlp(self.norm2(x))
      return x
  
file_path: MONAI/monai/networks/blocks/transformerblock.py
imports: from __future__ import annotations
  import torch.nn
  from monai.networks.blocks.mlp import MLPBlock
  from monai.networks.blocks.selfattention import SABlock
label_desc: Use image node_id 2 for calling the TransformerBlock obj's underlying member method code with example usage: obj.forward(x) and returns: x