class_docstr: Applies layer normalization by subtracting the mean from the inputs
  as described in the  `"Revisiting 'Over-smoothing' in Deep GCNs"
  <https://arxiv.org/pdf/2003.13663.pdf>`_ paper.
  
  .. math::
      \mathbf{x}_i = \mathbf{x}_i - \frac{1}{|\mathcal{V}|}
      \sum_{j \in \mathcal{V}} \mathbf{x}_j
code: def __repr__(self) -> str:
      return f"{self.__class__.__name__}()"
  
imports: from typing import Optional
  import torch
  from torch import Tensor
  from torch_geometric.utils import scatter
label_desc: Use image node_id 2 for calling the MeanSubtractionNorm obj's underlying member method code with example usage: obj.__repr__() and returns: self, str