code: def _len_guards(M):
      """Handle small or incorrect window lengths"""
      if int(M) != M or M < 0:
          raise ValueError(
              "Window length M must be a non-negative integer"
          )
      return M <= 1
  
imports: from __future__ import division, print_function, absolute_import
  import operator
  import warnings
  import numpy
  from scipy import fftpack, linalg, special
  from scipy._lib.six import string_types
label_desc: Use image node_id 1 for calling a global function with example usage: _len_guards(M) and returns: unknown