Update triviaqa.py

Removes the `_remove_prefixes` optimization as it's invalid for exact match metrics. Closes https://github.com/EleutherAI/lm-evaluation-harness/issues/726

lm_eval/tasks/triviaqa.py

@@ -28,7 +28,7 @@ _CITATION = """
 
 
 class TriviaQA(Task):
-    VERSION = 2
+    VERSION = 3
     DATASET_PATH = "trivia_qa"
     DATASET_NAME = "rc.nocontext"
 
@@ -62,16 +62,6 @@ class TriviaQA(Task):
     def doc_to_target(self, doc):
         return " " + doc["answer"]["value"]
 
-    def _remove_prefixes(self, aliases):
-        # Optimization: Remove any alias that has a strict prefix elsewhere in the list
-        # we can do this because if the prefix is acceptable by isgreedy, we can stop looking
-        aliases.sort()
-        ret = [aliases[0]]
-        for alias in aliases[1:]:
-            if not alias.startswith(ret[-1]):
-                ret.append(alias)
-        return ret
-
     def construct_requests(self, doc, ctx):
         """Uses RequestFactory to construct Requests and returns an iterable of
         Requests which will be sent to the LM.
@@ -87,7 +77,7 @@ class TriviaQA(Task):
 
     def process_results(self, doc, results):
         continuation = results[0].strip().lower().translate(str.maketrans('', '', string.punctuation))
-        list_of_candidates = [alias.lower().translate(str.maketrans('', '', string.punctuation)) for alias in self._remove_prefixes(doc["answer"]["aliases"])]
+        list_of_candidates = [alias.lower().translate(str.maketrans('', '', string.punctuation)) for alias in doc["answer"]["aliases"]]
         return {"em": float(continuation in list_of_candidates)}
 
     def aggregation(self):