docstr: Convenience function which TorchAgent calls to get current scale value.
code: def loss_scale(self):
      """
      Convenience function which TorchAgent calls to get current scale value.
      """
      return self.scaler.loss_scale
  
imports: import math
  from itertools import chain
  from typing import Optional
  import parlai.utils.logging
label_desc: Use image node_id 15 for calling the SafeFP16Optimizer obj's underlying member method code with example usage: obj.loss_scale() and returns: self