Fix layer integrated gradients pyre fixme issues (#1473)

Summary:

Fixing unresolved pyre fixme issues in corresponding file

Differential Revision: D67706224

Author: Vivek Miglani

captum/attr/_core/layer/layer_integrated_gradients.py

@@ -33,6 +33,7 @@
 )
 from captum.log import log_usage
 from torch import Tensor
+from torch.nn import Module
 from torch.nn.parallel.scatter_gather import scatter
 
 
@@ -58,8 +59,7 @@ class LayerIntegratedGradients(LayerAttribution, GradientAttribution):
 
     def __init__(
         self,
-        # pyre-fixme[24]: Generic type `Callable` expects 2 type parameters.
-        forward_func: Callable,
+        forward_func: Callable[..., Tensor],
         layer: ModuleOrModuleList,
         device_ids: Union[None, List[int]] = None,
         multiply_by_inputs: bool = True,
@@ -128,8 +128,7 @@ def _make_gradient_func(
     ) -> Callable[..., Tuple[Tensor, ...]]:
 
         def _gradient_func(
-            # pyre-fixme[24]: Generic type `Callable` expects 2 type parameters.
-            forward_fn: Callable,
+            forward_fn: Callable[..., Tensor],
             inputs: Union[Tensor, Tuple[Tensor, ...]],
             target_ind: TargetType = None,
             additional_forward_args: Optional[object] = None,
@@ -146,28 +145,21 @@ def _gradient_func(
                     target_gpus=self.device_ids,
                 )
 
-            scattered_inputs_dict = {
+            scattered_inputs_dict: Dict[
+                torch.device, Union[Tensor, Tuple[Tensor, ...]]
+            ] = {
                 scattered_input[0].device: scattered_input
                 for scattered_input in scattered_inputs
             }
 
             with torch.autograd.set_grad_enabled(True):
 
-                # pyre-fixme[53]: Captured variable `num_outputs_cumsum` is not
-                #  annotated.
-                # pyre-fixme[53]: Captured variable `scattered_inputs_dict` is not
-                #  annotated.
-                # pyre-fixme[3]: Return type must be annotated.
                 def layer_forward_hook(
-                    # pyre-fixme[2]: Parameter must be annotated.
-                    module,
-                    # pyre-fixme[2]: Parameter must be annotated.
-                    hook_inputs,
-                    # pyre-fixme[2]: Parameter must be annotated.
-                    hook_outputs=None,
-                    # pyre-fixme[2]: Parameter must be annotated.
-                    layer_idx=0,
-                ):
+                    module: Module,
+                    hook_inputs: Union[Tensor, Tuple[Tensor, ...]],
+                    hook_outputs: Union[None, Tensor, Tuple[Tensor, ...]] = None,
+                    layer_idx: int = 0,
+                ) -> Union[Tensor, Tuple[Tensor, ...]]:
                     device = _extract_device(module, hook_inputs, hook_outputs)
                     is_layer_tuple = (
                         isinstance(hook_outputs, tuple)
@@ -177,11 +169,14 @@ def layer_forward_hook(
                     )
 
                     if is_layer_tuple:
-                        return scattered_inputs_dict[device][
-                            num_outputs_cumsum[layer_idx] : num_outputs_cumsum[
-                                layer_idx + 1
-                            ]
-                        ]
+                        return cast(
+                            Union[Tensor, Tuple[Tensor, ...]],
+                            scattered_inputs_dict[device][
+                                num_outputs_cumsum[layer_idx] : num_outputs_cumsum[
+                                    layer_idx + 1
+                                ]
+                            ],
+                        )
 
                     return scattered_inputs_dict[device][num_outputs_cumsum[layer_idx]]
 
@@ -502,11 +497,22 @@ def attribute(
             additional_forward_args
         )
 
-        # pyre-fixme[3]: Return type must be annotated.
-        # pyre-fixme[2]: Parameter must be annotated.
-        def flatten_tuple(tup):
+        def flatten_tuple(tup: List[Tuple[Tensor, ...]]) -> Tuple[Tensor, ...]:
             return tuple(
-                sum((list(x) if isinstance(x, (tuple, list)) else [x] for x in tup), [])
+                cast(
+                    List[Tensor],
+                    sum(
+                        (
+                            (
+                                list(x)
+                                if isinstance(x, (tuple, list))
+                                else cast(List[Tensor], [x])
+                            )
+                            for x in tup
+                        ),
+                        [],
+                    ),
+                )
             )
 
         if self.device_ids is None:
@@ -520,16 +526,18 @@ def flatten_tuple(tup):
             additional_forward_args=additional_forward_args,
             attribute_to_layer_input=attribute_to_layer_input,
         )
-
+        input_layer_list: List[Tuple[Tensor, ...]]
         # if we have one output
         if not isinstance(self.layer, list):
-            inputs_layer = (inputs_layer,)
+            input_layer_list = [cast(Tuple[Tensor, ...], inputs_layer)]
+        else:
+            input_layer_list = inputs_layer
 
-        num_outputs = [1 if isinstance(x, Tensor) else len(x) for x in inputs_layer]
+        num_outputs = [1 if isinstance(x, Tensor) else len(x) for x in input_layer_list]
         num_outputs_cumsum = torch.cumsum(
             torch.IntTensor([0] + num_outputs), dim=0  # type: ignore
         )
-        inputs_layer = flatten_tuple(inputs_layer)
+        inputs_layer = flatten_tuple(input_layer_list)
 
         baselines_layer = _forward_layer_eval(
             self.forward_func,