AcceptabilityChecker min words adjustable (facebookresearch#3846)

* min words as a param

* min words as input param

* pr comment

parlai/crowdsourcing/utils/acceptability.py

@@ -19,9 +19,13 @@ class AcceptabilityChecker:
         'exact_match',
         'safety',
     ]
+    DEFAULT_MIN_WORDS_THRESHOLD = 3
 
-    def __init__(self):
+    def __init__(self, min_words: int = None):
         self.offensive_lang_detector = OffensiveStringMatcher()
+        self.min_words_violation_threshold = (
+            min_words or self.DEFAULT_MIN_WORDS_THRESHOLD
+        )
 
     def check_messages(
         self,
@@ -57,7 +61,7 @@ def check_messages(
         # Do messages have the minimum acceptable average number of words?
         if 'min_words' in violation_types:
             total_num_words = sum([len(message.split()) for message in messages])
-            if total_num_words / len(messages) < 3:
+            if total_num_words / len(messages) < self.min_words_violation_threshold:
                 violations.append('under_min_length')
 
         # Does the first message start with a greeting, indicating that the Turker