Fix neuron gradient shap pyre fixme issues (#1463)

Summary: Pull Request resolved: #1463

Differential Revision: D67705098

Author: Vivek Miglani

captum/attr/_core/neuron/neuron_gradient_shap.py

@@ -4,10 +4,11 @@
 from typing import Callable, List, Optional, Tuple, Union
 
 from captum._utils.gradient import construct_neuron_grad_fn
-from captum._utils.typing import TensorOrTupleOfTensorsGeneric
+from captum._utils.typing import SliceIntType, TensorOrTupleOfTensorsGeneric
 from captum.attr._core.gradient_shap import GradientShap
 from captum.attr._utils.attribution import GradientAttribution, NeuronAttribution
 from captum.log import log_usage
+from torch import Tensor
 from torch.nn import Module
 
 
@@ -50,8 +51,7 @@ class NeuronGradientShap(NeuronAttribution, GradientAttribution):
 
     def __init__(
         self,
-        # pyre-fixme[24]: Generic type `Callable` expects 2 type parameters.
-        forward_func: Callable,
+        forward_func: Callable[..., Union[int, float, Tensor]],
         layer: Module,
         device_ids: Union[None, List[int]] = None,
         multiply_by_inputs: bool = True,
@@ -97,8 +97,11 @@ def __init__(
     def attribute(
         self,
         inputs: TensorOrTupleOfTensorsGeneric,
-        # pyre-fixme[24]: Generic type `Callable` expects 2 type parameters.
-        neuron_selector: Union[int, Tuple[Union[int, slice], ...], Callable],
+        neuron_selector: Union[
+            int,
+            Tuple[Union[int, SliceIntType], ...],
+            Callable[[Union[Tensor, Tuple[Tensor, ...]]], Tensor],
+        ],
         baselines: Union[
             TensorOrTupleOfTensorsGeneric, Callable[..., TensorOrTupleOfTensorsGeneric]
         ],