code: def nanstd(
      a, axis=None, dtype=None, out=None, ddof=0, keepdims=False
  ):
      """Returns the standard deviation along an axis ignoring NaN values.
  
      Args:
          a (cupy.ndarray): Array to compute standard deviation.
          axis (int): Along which axis to compute standard deviation. The
              flattened array is used by default.
          dtype: Data type specifier.
          out (cupy.ndarray): Output array.
          keepdims (bool): If ``True``, the axis is remained as an axis of
              size one.
  
      Returns:
          cupy.ndarray: The standard deviation of the input array along the axis.
  
      .. seealso:: :func:`numpy.nanstd`
  
      """
      if a.dtype.kind in "biu":
          return a.std(
              axis=axis,
              dtype=dtype,
              out=out,
              ddof=ddof,
              keepdims=keepdims,
          )
  
      # TODO(okuta): check type
      return _statistics._nanstd(
          a,
          axis=axis,
          dtype=dtype,
          out=out,
          ddof=ddof,
          keepdims=keepdims,
      )
  
file_path: cupy/cupy/_statistics/meanvar.py
imports: import functools
  import numpy
  import cupy
  from cupy._core import _routines_statistics
label_desc: Use image node_id 9 for calling a global function with example usage: nanstd(a, axis, dtype, out, ddof, keepdims) and returns: _statistics, a