Fix class summarizer pyre fix me issues

Differential Revision: D67706853

Author: Vivek Miglani

captum/attr/_utils/class_summarizer.py

@@ -2,7 +2,7 @@
 
 # pyre-strict
 from collections import defaultdict
-from typing import Any, Dict, List, Optional, Union
+from typing import Any, cast, Dict, Generic, List, Optional, TypeVar, Union
 
 from captum._utils.common import _format_tensor_into_tuples
 from captum._utils.typing import TargetType, TensorOrTupleOfTensorsGeneric
@@ -11,8 +11,10 @@
 from captum.log import log_usage
 from torch import Tensor
 
+KeyType = TypeVar("KeyType")
 
-class ClassSummarizer(Summarizer):
+
+class ClassSummarizer(Summarizer, Generic[KeyType]):
     r"""
     Used to keep track of summaries for associated classes. The
     classes/labels can be of any type that are supported by `dict`.
@@ -23,8 +25,7 @@ class ClassSummarizer(Summarizer):
     @log_usage()
     def __init__(self, stats: List[Stat]) -> None:
         Summarizer.__init__.__wrapped__(self, stats)
-        # pyre-fixme[4]: Attribute annotation cannot contain `Any`.
-        self.summaries: Dict[Any, Summarizer] = defaultdict(
+        self.summaries: Dict[KeyType, Summarizer] = defaultdict(
             lambda: Summarizer(stats=stats)
         )
 
@@ -84,15 +85,15 @@ def update(  # type: ignore
             tensors_to_summarize_copy = tuple(tensor[i].clone() for tensor in x)
             label = labels_typed[0] if len(labels_typed) == 1 else labels_typed[i]
 
-            self.summaries[label].update(tensors_to_summarize)
+            self.summaries[cast(KeyType, label)].update(tensors_to_summarize)
             super().update(tensors_to_summarize_copy)
 
     @property
-    # pyre-fixme[3]: Return annotation cannot contain `Any`.
     def class_summaries(
         self,
     ) -> Dict[
-        Any, Union[None, Dict[str, Optional[Tensor]], List[Dict[str, Optional[Tensor]]]]
+        KeyType,
+        Union[None, Dict[str, Optional[Tensor]], List[Dict[str, Optional[Tensor]]]],
     ]:
         r"""
         Returns: