code: def _make_production_string(source, target):
      return "{source} -> {target}"
  
imports: from __future__ import absolute_import
  from collections import defaultdict
  from nltk.sem.logic import Expression, ApplicationExpression, ConstantExpression, LogicParser, Variable
  from nltk.sem.logic import Type, BasicType, ComplexType, ANY_TYPE
  from allennlp.common.util import START_SYMBOL
label_desc: Use image node_id 2 for calling a global function with example usage: _make_production_string(source, target) and returns: str