Simplify axis value checks (#1501)

torchaudio/functional/functional.py

@@ -732,7 +732,7 @@ def mask_along_axis_iid(
         Tensor: Masked spectrograms of dimensions (batch, channel, freq, time)
     """
 
-    if axis != 2 and axis != 3:
+    if axis not in [2, 3]:
         raise ValueError('Only Frequency and Time masking are supported')
 
     device = specgrams.device
@@ -774,7 +774,7 @@ def mask_along_axis(
     Returns:
         Tensor: Masked spectrogram of dimensions (channel, freq, time)
     """
-    if axis != 1 and axis != 2:
+    if axis not in [1, 2]:
         raise ValueError('Only Frequency and Time masking are supported')
 
     # pack batch