code: def test_nograd(self):
      x = Tensor(x_init, requires_grad=False)
      m = Tensor(m_init, requires_grad=False)
      W = Tensor(W_init, requires_grad=True)
      tmp = x.mul(m)
      mm = tmp.matmul(W)
      out = mm.relu()
      out = out.sum()
      out.backward()
      assert x.grad is None
      assert m.grad is None
      assert tmp.grad is None
      assert mm.grad is not None
      assert W.grad is not None
  
imports: import numpy
  import torch
  import unittest, copy
  import mmap
  from tinygrad import Tensor, Device, dtypes
  from tinygrad.helpers import temp
  from extra.gradcheck import numerical_jacobian, jacobian, gradcheck
label_desc: Use image node_id 5 for calling the TestTinygrad obj's underlying member method code with example usage: obj.test_nograd() without return types