code: def test_external_std_all_ddof(self, xp, dtype):
      a = testing.shaped_arange((2, 3), xp, dtype)
      return xp.std(a, ddof=1)
  
imports: import math
  import numpy
  import pytest
  import cupy
  from cupy import testing
label_desc: Use image node_id 19 for calling the TestMeanVar obj's underlying member method code with example usage: obj.test_external_std_all_ddof(xp, dtype) and returns: xp