code: def _unitary(norm):
      if norm not in (None, "ortho"):
          raise ValueError(
              'Invalid norm value %s, should be None or "ortho".' % norm
          )
      return norm is not None
  
imports: from __future__ import division, absolute_import, print_function
  import functools
  from numpy.core import array, asarray, zeros, swapaxes, shape, conjugate, take, sqrt
  from numpy.core.multiarray import normalize_axis_index
  from numpy.core import overrides
  from .None import fftpack_lite
  from .helper import _FFTCache
label_desc: Use image node_id 2 for calling a global function with example usage: _unitary(norm) and returns: unknown