code: def model_grads_to_main_grads(model, main_params):
      main_params.grad.data.copy_(
          _flatten_dense_tensors(
              [
                  p.grad.data
                  for p in model.parameters()
                  if p.requires_grad
              ]
          )
      )
  
imports: import torch
  import torch.nn
  from torch._utils import _flatten_dense_tensors, _unflatten_dense_tensors
label_desc: Use image node_id 7 for calling a global function with example usage: model_grads_to_main_grads(model, main_params) without return types