code: def test_diag_construction(self, xp):
      a = testing.shaped_arange((3,), xp)
      r = xp.diag(a)
      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 6 for calling the TestMatrix obj's underlying member method code with example usage: obj.test_diag_construction(xp) and returns: r