class_docstr: Patch Merging Layer.
  
  Args:
      input_resolution (tuple[int]): Resolution of input feature.
      dim (int): Number of input channels.
      norm_layer (nn.Module, optional): Normalization layer.  Default: nn.LayerNorm
code: def extra_repr(self) -> str:
      return f"input_resolution={self.input_resolution}, dim={self.dim}"
  
imports: from typing import List, Optional
  import torch
  import torch.nn
  import torch.utils.checkpoint
  from vissl.config import AttrDict
  from vissl.models.model_helpers import DropPath, to_2tuple, trunc_normal_
  from vissl.models.trunks import register_model_trunk
label_desc: Use image node_id 3 for calling the PatchMerging obj's underlying member method code with example usage: obj.extra_repr() and returns: str, self, str, self