Add an identity decoder field to the volumetric_models decoder config.

PiperOrigin-RevId: 382051540

official/vision/beta/projects/volumetric_models/configs/decoders.py

@@ -21,6 +21,12 @@ import dataclasses
 from official.modeling import hyperparams
 
 
+@dataclasses.dataclass
+class Identity(hyperparams.Config):
+  """Identity config."""
+  pass
+
+
 @dataclasses.dataclass
 class UNet3DDecoder(hyperparams.Config):
   """UNet3D decoder config."""
@@ -37,7 +43,9 @@ class Decoder(hyperparams.OneOfConfig):
 
   Attributes:
     type: 'str', type of decoder be used, on the of fields below.
-    fpn: fpn config.
+    identity: identity decoder config.
+    unet_3d_decoder: UNet3D decoder config.
   """
   type: Optional[str] = None
+  identity: Identity = Identity()
   unet_3d_decoder: UNet3DDecoder = UNet3DDecoder()