code: def single(x):
      if len(x) != 1:
          raise Exception("Length of {} is not equal to 1".format(x))
      return x[0]
  
imports: import functools
  import threading
  import collections
  import contextlib
  import six
label_desc: Use image node_id 2 for calling a global function with example usage: single(x) and returns: x