code: def test_zscore_nan_policy_omit_axis_ddof(self, xp, scp, dtype):
      x = xp.array([4.0, 1.0, 1.0, xp.nan], dtype=dtype)
      return scp.stats.zscore(x, axis=0, ddof=1, nan_policy="omit")
  
imports: import numpy
  import pytest
  import cupy
  from cupy import testing
  import cupyx
  import cupyx.scipy.stats
label_desc: Use image node_id 12 for calling the TestZscore obj's underlying member method code with example usage: obj.test_zscore_nan_policy_omit_axis_ddof(xp, scp, dtype) and returns: scp