code: def is_rel(s):
      """
      Check whether a set represents a relation (of any arity).
  
      :param s: a set containing tuples of str elements
      :type s: set
      :rtype: bool
      """
      # we have the empty relation, i.e. set()
      if len(s) == 0:
          return True
      # all the elements are tuples of the same length
      elif all(isinstance(el, tuple) for el in s) and len(
          max(s)
      ) == len(min(s)):
          return True
      else:
          raise ValueError(
              "Set %r contains sequences of different lengths" % s
          )
  
imports: import inspect
  import re
  import sys
  import textwrap
  from pprint import pformat
  from nltk.decorators import decorator
  from nltk.sem.logic import AbstractVariableExpression, AllExpression, AndExpression, ApplicationExpression, EqualityExpression, ExistsExpression, Expression, IffExpression, ImpExpression, IndividualVariableExpression, IotaExpression, LambdaExpression, NegatedExpression, OrExpression, Variable, is_indvar
label_desc: Use image node_id 2 for calling a global function with example usage: is_rel(s) and returns: True, True