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
code: def __str__(self):
      return f"IndexMapper(input_size={self.input_size}, output_size={self.output_size})"
  
imports: import itertools
  import numpy
label_desc: Use image node_id 5 for calling the IndexMapper obj's underlying member method code with example usage: obj.__str__() and returns: str, self, str, self, str