code: def pre_zero_grad(self) -> None:
      pass
  
file_path: ColossalAI/colossalai/amp/naive_amp/mixed_precision_mixin/bf16.py
imports: import torch
  from torch import Tensor
  from .base import MixedPrecisionMixin
label_desc: Use image node_id 4 for calling the BF16MixedPrecisionMixin obj's underlying member method code with example usage: obj.pre_zero_grad() without return types