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 hybrid_forward(
      self,
      F,
      data: Tensor,
      observed_indicator: Tensor,
      scale: Optional[Tensor],
      rep_params: List[Tensor],
      **kwargs,
  ) -> Tuple[Tensor, Tensor, List[Tensor]]:
      data = F.expand_dims(data, axis=self.axis)
      return data, scale, rep_params
  
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 2 for calling the DimExpansion obj's underlying member method code with example usage: obj.hybrid_forward(F, data, observed_indicator, scale, rep_params) and returns: data,  scale,  rep_params