class_docstr: A simple class that allows us to wrap multiple optimizers into a single API typical of a single
  optimizer, with ``zero_grad`` and ``step`` methods.
  
  Parameters
  ----------
  optimizers: List of ``torch.optim.Optimizer``s
docstr: Apply ``zero_grad`` to all optimizers.
docstr_tok: ["Apply","``","zero_grad","``","to","all","optimizers","."]
code: def zero_grad(self) -> None:
      """Apply ``zero_grad`` to all optimizers."""
      for optimizer in self.optimizers:
          optimizer.zero_grad()
  
file_path: collie/collie/model/base/layers.py
imports: from typing import Dict, List
  import torch
label_desc: Use image node_id 2 for calling the MultiOptimizer obj's underlying member method code with example usage: obj.zero_grad() without return types