class_docstr: A class representing a dimension expansion operation along a specified
  axis.
  
  Parameters
  ----------
  axis
      Axis on which to expand the tensor.
      (default: -1)
code: def __init__(self, axis: int = -1, *args, **kwargs):
      super().__init__(*args, **kwargs)
      self.axis = axis
  
imports: from typing import List, Optional, Tuple
  from gluonts.core.component import validated
  from gluonts.mx import Tensor
  from .representation import Representation
label_desc: Use image node_id 1 to create a new DimExpansion object from inherited base classes: Representation with example: obj = DimExpansion(axis)