class_docstr: Test class for scipy.stats.variation
code: def test_ddof(self):
      x = np.arange(9.0)
      assert_allclose(variation(x, ddof=1), np.sqrt(60 / 8) / 4)
  
imports: import numpy
  from numpy.testing import assert_equal, assert_allclose
  import pytest
  from scipy.stats import variation
  from scipy._lib._util import AxisError
label_desc: Use image node_id 1 for calling the TestVariation obj's underlying member method code with example usage: obj.test_ddof() without return types