Fix some docstrings (#996)

Summary:
The "optional" part should come last.

Pull Request resolved: #996

Reviewed By: 99warriors, Reubend

Differential Revision: D38026646

Pulled By: NarineK

fbshipit-source-id: 6648b3a2183dd4c8d29956e356f1ac5cd90d23cd

Author: ProGamerGov

captum/attr/_core/lime.py

@@ -734,7 +734,7 @@ def __init__(
 
             forward_func (callable):  The forward function of the model or any
                     modification of it
-            interpretable_model (optional, Model): Model object to train
+            interpretable_model (Model, optional): Model object to train
                     interpretable model.
 
                     This argument is optional and defaults to SkLearnLasso(alpha=0.01),
@@ -760,7 +760,7 @@ def __init__(
                     Note that calling fit multiple times should retrain the
                     interpretable model, each attribution call reuses
                     the same given interpretable model object.
-            similarity_func (optional, callable): Function which takes a single sample
+            similarity_func (callable, optional): Function which takes a single sample
                     along with its corresponding interpretable representation
                     and returns the weight of the interpretable sample for
                     training the interpretable model.
@@ -793,7 +793,7 @@ def __init__(
 
                     kwargs includes baselines, feature_mask, num_interp_features
                     (integer, determined from feature mask).
-            perturb_func (optional, callable): Function which returns a single
+            perturb_func (callable, optional): Function which returns a single
                     sampled input, which is a binary vector of length
                     num_interp_features, or a generator of such tensors.
 

captum/robust/_core/metrics/attack_comparator.py

@@ -118,7 +118,7 @@ def add_attack(
                 or any other perturbation or attack function such
                 as a torchvision transform.
 
-            name (optional, str): Name or identifier for attack, used as key for
+            name (str, optional): Name or identifier for attack, used as key for
                 attack results. This defaults to attack.__class__.__name__
                 if not provided and must be unique for all added attacks.