class_docstr: Adadelta implementation for SGD: http://arxiv.org/abs/1212.5701
  
  :param decayrate interpolation parameter rho
  :param epsilon for numerical stability
  >>> adagrad = Adadelta()
  creating: createAdadelta
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 Adadelta obj's underlying member method code with example usage: obj.get_optimizer() and returns: self