code: def step(self, gradient):
      # logger.info(f"before copy, model parameter: {self.model_parameter}")
      self.prev_model_parameter = self.model_parameter.data.clone()
      self.model_parameter.grad = gradient
      self.optimizer.step()
  
imports: import logging
  import numpy
  import torch
label_desc: Use image node_id 3 for calling the Optimizer obj's underlying member method code with example usage: obj.step(gradient) without return types