code: def test_at(arr):
      assert m.at_t(arr, 0, 2) == 3
      assert m.at_t(arr, 1, 0) == 4
  
      assert all(m.mutate_at_t(arr, 0, 2).ravel() == [1, 2, 4, 4, 5, 6])
      assert all(m.mutate_at_t(arr, 1, 0).ravel() == [1, 2, 4, 5, 5, 6])
  
imports: import pytest
  import env
  from pybind11_tests import numpy_array
label_desc: Use image node_id 8 for calling a global function with example usage: test_at(arr) without return types