Error integrating with puddle-world

From Cathy

```
Traceback (most recent call last):
File "ecLearner.py", line 513, in
**args)
File "../ec/dreamcoder/ec.py", line 130, in explorationCompression
for r in ecIterator(*arguments, **keywords):
File "../ec/dreamcoder/ec.py", line 411, in ecIterator
result=result)
File "ecLearner.py", line 315, in wake_generative_with_pyccg
if self.use_pyccg_enum: self._update_pyccg_with_supervised_batch(fallback_frontiers)
File "ecLearner.py", line 225, in _update_pyccg_with_supervised_batch
self.pyccg_learner.update_with_supervision(instruction, model, converted_pyccg)
File "../pyccg/pyccg/word_learner.py", line 307, in update_with_supervision
self.lexicon = augment_lexicon_unification(self.lexicon, sentence, self.ontology, lf)
File "../pyccg/pyccg/lexicon.py", line 836, in augment_lexicon_unification
candidate_parses = list(candidate_parses)
File "../pyccg/pyccg/lexicon.py", line 719, in attempt_candidate_parse
category_sem_arities = lexicon.category_semantic_arities()
File "../pyccg/pyccg/lexicon.py", line 312, in category_semantic_arities
ret[category] = set(get_arity(entry.semantics()) for entry in entries)
File "../pyccg/pyccg/lexicon.py", line 312, in
ret[category] = set(get_arity(entry.semantics()) for entry in entries)
File "../pyccg/pyccg/logic.py", line 2667, in get_expr_arity
return 1 + self.get_expr_arity(expr.term)
File "../pyccg/pyccg/logic.py", line 2667, in get_expr_arity
return 1 + self.get_expr_arity(expr.term)
File "../pyccg/pyccg/logic.py", line 2667, in get_expr_arity
return 1 + self.get_expr_arity(expr.term)
File "../pyccg/pyccg/logic.py", line 2669, in get_expr_arity
function = self.functions_dict[expr.pred.variable.name]
KeyError: 'z2'
```