code: def validate_func(x, allow_none=True):
      if not (allow_none and x is None) and hasattr(x, "__call__"):
          raise ValueError("'%s' must be a function." % x.__name__)
  
imports: from __future__ import division, print_function, absolute_import
  import six
  import string
  import random
  import numpy
  import tensorflow.compat.v1
  from tensorflow.python import pywrap_tensorflow
  import tflearn.variables
label_desc: Use image node_id 34 for calling a global function with example usage: validate_func(x, allow_none) without return types