code: def test_diag_construction_from_list(self, xp):
      a = [1, 2, 3]
      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 7 for calling the TestMatrix obj's underlying member method code with example usage: obj.test_diag_construction_from_list(xp) and returns: r