class_docstr: Test class for scipy.stats.variation
code: def test_nan_policy_raise(self):
      x = np.array([1.0, 2.0, np.nan, 3.0])
      with pytest.raises(ValueError, match="input contains nan"):
          variation(x, nan_policy="raise")
  
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 5 for calling the TestVariation obj's underlying member method code with example usage: obj.test_nan_policy_raise() without return types