class_docstr: Base layer class.
  
  Parameters
  ----------
  input_size : list
      size of the layer input
  output_size : list
      size of the layer output
  activation : str or None
      activation function name
  input_index_mapper : IndexMapper or None
      map indexes from this layer index to the input layer index size
docstr: Return the size of the output tensor
docstr_tok: ["Return","the","size","of","the","output","tensor"]
code: def output_size(self):
      """Return the size of the output tensor"""
      return self.__output_size
  
imports: import itertools
  import numpy
label_desc: Use image node_id 3 for calling the Layer obj's underlying member method code with example usage: obj.output_size() and returns: self