Add get_city_name() method to dataloader, to fetch name of city where a log was captured.

src/av2/datasets/sensor/av2_sensor_dataloader.py

@@ -46,10 +46,6 @@ def __init__(self, data_dir: Path, labels_dir: Path) -> None:
         self._labels_dir = labels_dir
         self._sdb = SynchronizationDB(str(data_dir))
 
-    def get_city_name(self, log_id: str) -> str:
-        """Return the name of the city where the log of interest was captured."""
-        raise NotImplementedError("Method is not available yet.")
-
     def get_log_pinhole_camera(self, log_id: str, cam_name: str) -> PinholeCamera:
         """Return a PinholeCamera parameterized by sensor pose in vehicle frame, intrinsics, and image dimensions."""
         log_dir = self._data_dir / log_id
@@ -136,6 +132,28 @@ def get_log_map_dirpath(self, log_id: str) -> Path:
         """Fetch the path to the directory containing map files for a single vehicle log."""
         return self._data_dir / log_id / "map"
 
+    def get_city_name(self, log_id: str) -> str:
+        """Return the name of the city where the log of interest was captured.
+
+        Vector map filenames contain the city name, and have a name in the following format:
+            `log_map_archive_453e5558-6363-38e3-bf9b-42b5ba0a6f1d____PAO_city_71741.json`
+
+        Args:
+            log_id: unique ID of vehicle log.
+
+        Returns:
+            Name of the city where the log of interest was captured.
+
+        Raises:
+            RuntimeError: If no vector map file is found for the query log ID.
+        """
+        vector_map_fpaths = list(self._data_dir.glob(f"{log_id}/map/log_map_archive*"))
+        if len(vector_map_fpaths) != 1:
+            raise RuntimeError(f"Vector map file is missing for {log_id}")
+        vector_map_fpath = vector_map_fpaths[0]
+        log_city_name = vector_map_fpath.name.split("____")[1].split("_")[0]
+        return log_city_name
+
     def get_log_ids(self) -> List[str]:
         """Return a list of all vehicle log IDs available at the provided dataroot."""
         return sorted([d.name for d in self._data_dir.glob("*") if d.is_dir()])