class_docstr: Class implementing the GEMM strategy (in PyTorch) for GBDT models.
code: def aggregation(self, x):
      output = (
          torch.squeeze(x)
          .t()
          .view(-1, self.n_gbdt_classes, self.n_trees_per_class)
          .sum(2)
      )
  
      return self.post_transform(output)
  
imports: from abc import abstractmethod
  from enum import Enum
  import numpy
  import torch
  from .None import constants
  from ._physical_operator import PhysicalOperator
  from .None import _tree_commons
label_desc: Use image node_id 2 for calling the GEMMGBDTImpl obj's underlying member method code with example usage: obj.aggregation(x) and returns: self