Add transformation filters: lowercase, uppercase, map

lm_eval/filters/__init__.py

 from lm_eval.api.filter import FilterEnsemble
 from . import selection
 from . import extraction
+from . import transformation
 
 
 FILTER_REGISTRY = {
@@ -9,6 +10,9 @@ FILTER_REGISTRY = {
     "majority_vote": selection.MajorityVoteFilter,
     "take_first_k": selection.TakeKFilter,
     "remove_whitespace": extraction.WhitespaceFilter,
+    "lowercase": transformation.LowercaseFilter,
+    "uppercase": transformation.UppercaseFilter,
+    "map": transformation.MapFilter,
     # TODO: implement this filter. either it should take in an arbitrary "scoring"/reward function
     # that takes an input and returns a scalar and then should select the max reward,
     # or should implement different filters for different ways of handling a reward model's inference.

lm_eval/filters/transformation.py

+from lm_eval.api.filter import Filter
+
+
+class LowercaseFilter(Filter):
+    def __init__(self) -> None:
+        pass
+
+    def apply(self, resps, docs):
+        def filter_set(inst):
+            return [resp.lower() for resp in inst]
+
+        return [filter_set(resp) for resp in resps]
+
+ 
+class UppercaseFilter(Filter):
+    def __init__(self) -> None:
+        pass
+
+    def apply(self, resps, docs):
+        def filter_set(inst):
+            return [resp.upper() for resp in inst]
+
+        return [filter_set(resp) for resp in resps]
+        
+class MapFilter(Filter):
+    def __init__(self, mapping_dict: dict = {}, default_value = None) -> None:
+        """
+        Initializes the MapFilter with a given mapping dictionary and default value.
+
+        Args:
+        - mapping_dict (dict): A dictionary containing the key-value mappings.
+                               Default is an empty dictionary.
+        - default_value (Any): The value to be returned when a key is not found in the mapping_dict.
+                               Default is None.
+
+        Example:
+        mapper = MapFilter({'A': 1, 'B': 2}, default_value=0)
+        """
+        assert isinstance(mapping_dict, dict), "Provided mapping_dict is not a dictionary"
+        self.mapping_dict = mapping_dict
+        self.default_value = default_value
+
+    def apply(self, resps, docs):
+        def filter_set(inst):
+            return [self.mapping_dict.get(resp, self.default_value) for resp in inst]
+
+        return [filter_set(resp) for resp in resps]