class_docstr: An implementation of Adam http://arxiv.org/pdf/1412.6980.pdf
  :param learningrate learning rate
  :param learningrate_decay learning rate decay
  :param beta1 first moment coefficient
  :param beta2 second moment coefficient
  :param epsilon for numerical stability
  >>> pAdam = ParallelAdam()
  creating: createParallelAdam
code: def get_optimizer(self):
      return self.optimizer
  
imports: from abc import ABC, abstractmethod
  from bigdl.util.common import DOUBLEMAX
  from zoo.orca.learn.optimizers.schedule import Scheduler
label_desc: Use image node_id 2 for calling the ParallelAdam obj's underlying member method code with example usage: obj.get_optimizer() and returns: self