change mathqa to use numeric answer strings instead of a,b,c,d,e as choices

lm_eval/tasks/mathqa.py

 from . common import HFTask
 from lm_eval.base import mean, rf, MultipleChoiceTask
-
+import re
 
 class MathQA(HFTask, MultipleChoiceTask):
     DATASET_PATH = "math_qa"
@@ -17,10 +17,13 @@ class MathQA(HFTask, MultipleChoiceTask):
 
     def _convert_standard(self, doc):
 
+        answer_idx = ['a', 'b', 'c', 'd', 'e'].index(doc['correct'])
+        choices = [c[4:].rstrip(" ,") for c in re.findall(r"[abcd] \) .*?, |e .*?$", doc['options'])]
+
         out_doc = {
-            "query": "Question: " + doc['Problem'] +" "+ doc["options"] + "\nAnswer:",
-            "choices": ['a', 'b', 'c', 'd', 'e'],
-            "gold": ['a', 'b', 'c', 'd', 'e'].index(doc['correct']),
+            "query": "Question: " + doc['Problem'] +"\nAnswer:",
+            "choices": choices,
+            "gold": answer_idx,
         }
         return out_doc