class_docstr: A learning rate decay policy, where the effective learning rate is
  calculated as base_lr * gamma ^ (floor(iter / step_size))
  
  :param step_size
  :param gamma
  
  >>> step = Default()
  creating: createDefault
code: def get_scheduler(self):
      return self.scheduler
  
imports: from abc import ABC, abstractmethod
label_desc: Use image node_id 2 for calling the Default obj's underlying member method code with example usage: obj.get_scheduler() and returns: self