code: def test_diag_extraction_from_nested_tuple(self, xp):
      a = ((1, 2, 3), (4, 5, 6), (7, 8, 9))
      r = xp.diag(a, -1)
      assert isinstance(r, xp.ndarray)
      return r
  
imports: import unittest
  import numpy
  import pytest
  import cupy
  from cupy import testing
label_desc: Use image node_id 5 for calling the TestMatrix obj's underlying member method code with example usage: obj.test_diag_extraction_from_nested_tuple(xp) and returns: r