Fix gradcam pyre fixme issues (pytorch#1466)

Summary:


Fixing unresolved pyre fixme issues in corresponding file

Reviewed By: cyrjano

Differential Revision: D67705191

captum/attr/_core/layer/grad_cam.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 
 # pyre-strict
-from typing import Any, Callable, Dict, List, Optional, Tuple, Union
+from typing import Any, Callable, cast, Dict, List, Optional, Tuple, Union
 
 import torch
 import torch.nn.functional as F
@@ -54,8 +54,7 @@ class LayerGradCam(LayerAttribution, GradientAttribution):
 
     def __init__(
         self,
-        # pyre-fixme[24]: Generic type `Callable` expects 2 type parameters.
-        forward_func: Callable,
+        forward_func: Callable[..., Tensor],
         layer: Module,
         device_ids: Union[None, List[int]] = None,
     ) -> None:
@@ -201,7 +200,7 @@ def attribute(
         # hidden layer and hidden layer evaluated at each input.
         layer_gradients, layer_evals = compute_layer_gradients_and_eval(
             self.forward_func,
-            self.layer,
+            cast(Module, self.layer),
             inputs,
             target,
             additional_forward_args,
@@ -213,10 +212,7 @@ def attribute(
         summed_grads = tuple(
             (
                 torch.mean(
-                    # pyre-fixme[6]: For 1st argument expected `Tensor` but got
-                    #  `Tuple[Tensor, ...]`.
                     layer_grad,
-                    # pyre-fixme[16]: `tuple` has no attribute `shape`.
                     dim=tuple(x for x in range(2, len(layer_grad.shape))),
                     keepdim=True,
                 )
@@ -228,27 +224,15 @@ def attribute(
 
         if attr_dim_summation:
             scaled_acts = tuple(
-                # pyre-fixme[58]: `*` is not supported for operand types
-                #  `Union[tuple[torch._tensor.Tensor], torch._tensor.Tensor]` and
-                #  `Tuple[Tensor, ...]`.
-                # pyre-fixme[6]: For 1st argument expected `Tensor` but got
-                #  `Tuple[Tensor, ...]`.
                 torch.sum(summed_grad * layer_eval, dim=1, keepdim=True)
                 for summed_grad, layer_eval in zip(summed_grads, layer_evals)
             )
         else:
             scaled_acts = tuple(
-                # pyre-fixme[58]: `*` is not supported for operand types
-                #  `Union[tuple[torch._tensor.Tensor], torch._tensor.Tensor]` and
-                #  `Tuple[Tensor, ...]`.
                 summed_grad * layer_eval
                 for summed_grad, layer_eval in zip(summed_grads, layer_evals)
             )
 
         if relu_attributions:
-            # pyre-fixme[6]: For 1st argument expected `Tensor` but got
-            #  `Union[tuple[Tensor], Tensor]`.
             scaled_acts = tuple(F.relu(scaled_act) for scaled_act in scaled_acts)
-        # pyre-fixme[6]: For 2nd argument expected `Tuple[Tensor, ...]` but got
-        #  `Tuple[Union[tuple[Tensor], Tensor], ...]`.
         return _format_output(len(scaled_acts) > 1, scaled_acts)