Add Metadata Handling to Cameras Collation Function (#2001)

* Add metadata collate for cameras

* checks passed

---------

Co-authored-by: Matthew Tancik <tancik@berkeley.edu>

nerfstudio/data/utils/nerfstudio_collate.py

@@ -162,6 +162,13 @@ def nerfstudio_collate(batch: Any, extra_mappings: Union[Dict[type, Callable], N
         else:
             op = torch.cat
 
+        # Create metadata dictionary
+        metadata_keys = batch[0].metadata.keys()
+        assert all(
+            (cam.metadata.keys() == metadata_keys for cam in batch)
+        ), "All cameras must have the same metadata keys."
+        metadata = {key: op([cam.metadata[key] for cam in batch], dim=0) for key in metadata_keys}
+
         return Cameras(
             op([cameras.camera_to_worlds for cameras in batch], dim=0),
             op([cameras.fx for cameras in batch], dim=0),
@@ -184,6 +191,7 @@ def nerfstudio_collate(batch: Any, extra_mappings: Union[Dict[type, Callable], N
                 [cameras.times if cameras.times is not None else -torch.ones_like(cameras.times) for cameras in batch],
                 dim=0,
             ),
+            metadata=metadata,
         )
 
     for type_key in extra_mappings: