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 a list of the input indexes
docstr_tok: ["Return","a","list","of","the","input","indexes"]
code: def input_indexes(self):
      """Return a list of the input indexes"""
      return list(
          itertools.product(*[range(v) for v in self.__input_size])
      )
  
imports: import itertools
  import numpy
label_desc: Use image node_id 8 for calling the Layer obj's underlying member method code with example usage: obj.input_indexes() and returns: list