[fbsync] Adding _log_api_usage_once to Swin's reusable components. (#6174)

Reviewed By: datumbox

Differential Revision: D37212662

fbshipit-source-id: 051c69540c15723d3ce0780b8fcba5693cc9114a

Author: NicolasHug

torchvision/models/swin_transformer.py

@@ -34,6 +34,7 @@ class PatchMerging(nn.Module):
 
     def __init__(self, dim: int, norm_layer: Callable[..., nn.Module] = nn.LayerNorm):
         super().__init__()
+        _log_api_usage_once(self)
         self.dim = dim
         self.reduction = nn.Linear(4 * dim, 2 * dim, bias=False)
         self.norm = norm_layer(4 * dim)
@@ -268,6 +269,7 @@ def __init__(
         attn_layer: Callable[..., nn.Module] = ShiftedWindowAttention,
     ):
         super().__init__()
+        _log_api_usage_once(self)
 
         self.norm1 = norm_layer(dim)
         self.attn = attn_layer(