docstr: Return the optimizer's state dict.
code: def state_dict(self):
      """
      Return the optimizer's state dict.
      """
      state_dict = self.optimizer.state_dict()
      if self.scaler is not None:
          state_dict["loss_scaler"] = self.scaler.loss_scale
      return state_dict
  
imports: import math
  from itertools import chain
  from typing import Optional
  import parlai.utils.logging
label_desc: Use image node_id 4 for calling the SafeFP16Optimizer obj's underlying member method code with example usage: obj.state_dict() and returns: state_dict