code: def test_nanstd(self, xp, dtype):
      a = testing.shaped_random(self.shape, xp, dtype=dtype)
      if a.dtype.kind not in "biu":
          a[0, :] = xp.nan
      return xp.nanstd(
          a, axis=self.axis, ddof=self.ddof, keepdims=self.keepdims
      )
  
imports: import math
  import numpy
  import pytest
  import cupy
  from cupy import testing
label_desc: Use image node_id 2 for calling the TestNanVarStd obj's underlying member method code with example usage: obj.test_nanstd(xp, dtype) and returns: xp