code: def trainable_params(m:nn.Module)->ParamList:
      "Return list of trainable params in `m`."
      res = filter(lambda p: p.requires_grad, m.parameters())
      return ref trainable_params(m:nn.Module)->ParamList:
      "Return list of trainable params in `m`."
      res = filter(lambda p: p.requires_grad, m.parameters())
      return res
docs: Return list of trainable params in `m`.