class_docstr: Map indexes from one layer to the other.
  
  Parameters
  ----------
  input_size : tuple
      the input size
  output_size : tuple
      the mapped input layer's output size
docstr: Return the size of the input tensor
docstr_tok: ["Return","the","size","of","the","input","tensor"]
code: def input_size(self):
      """Return the size of the input tensor"""
      return self.__input_size
  
imports: import itertools
  import numpy
label_desc: Use image node_id 2 for calling the IndexMapper obj's underlying member method code with example usage: obj.input_size() and returns: self