code: def zero_grad(self):
      for param in self.params:
          param.grad = None
  
file_path: tinygrad/tinygrad/nn/optim.py
imports: from typing import List
  from tinygrad.helpers import dedup, getenv
  from tinygrad.tensor import Tensor
label_desc: Use image node_id 2 for calling the Optimizer obj's underlying member method code with example usage: obj.zero_grad() without return types