class_docstr: This class just allows us to implement ``Registrable`` for Pytorch :class:`LRSchedulers`.
code: def step(self, metric, epoch=None):
      raise NotImplementedError
  
imports: from __future__ import absolute_import
  import torch.optim.lr_scheduler
  from allennlp.common.checks import ConfigurationError
  from allennlp.common.params import Params
  from allennlp.common.registrable import Registrable
label_desc: Use image node_id 2 for calling the LearningRateScheduler obj's underlying member method code with example usage: obj.step(metric, epoch) without return types