class_docstr: [[Exponential]] is a learning rate schedule, which rescale the learning rate by
  lr_{n + 1} = lr * decayRate `^` (iter / decayStep)
  :param decay_step the inteval for lr decay
  :param decay_rate decay rate
  :param stair_case if true, iter / decayStep is an integer division
                   and the decayed learning rate follows a staircase function.
  
  >>> exponential = Exponential(100, 0.1)
  creating: createExponential
code: def get_scheduler(self):
      return self.scheduler
  
imports: from abc import ABC, abstractmethod
label_desc: Use image node_id 2 for calling the Exponential obj's underlying member method code with example usage: obj.get_scheduler() and returns: self