code: def forward(self, x_or_x_list):
      if isinstance(x_or_x_list, Tensor):
          return super().forward(x_or_x_list)
      elif isinstance(x_or_x_list, list):
          if not XFORMERS_AVAILABLE:
              raise AssertionError(
                  "xFormers is required for using nested tensors"
              )
          return self.forward_nested(x_or_x_list)
      else:
          raise AssertionError
  
imports: import logging
  import os
  from typing import Callable, List, Any, Tuple, Dict
  import warnings
  import torch
  from torch import nn, Tensor
  from .attention import Attention, MemEffAttention
  from .drop_path import DropPath
  from .layer_scale import LayerScale
  from .mlp import Mlp
label_desc: Use image node_id 2 for calling the NestedTensorBlock obj's underlying member method code with example usage: obj.forward(x_or_x_list) and returns: super, self