docs: def _load_isd_file_metadata(download_path, isd_station_metadata):
      """ Collect data counts for isd files.
      """
  
      isd_inventory = pd.read_csv(
          os.path.join(download_path, "isd-inventory.csv"), dtype=str
      )
  
      # filter to stations with metadata
      station_keep = [usaf in isd_station_metadata for usaf in isd_inventory.USAF]
      isd_inventory = isd_inventory[station_keep]
      # filter by year
      year_keep = isd_inventory.YEAR > "2005"
      isd_inventory = isd_inventory[year_keep]
  
      metadata = {}
      for (usaf_station, year), group in isd_inventory.groupby(["USAF", "YEAR"]):
          if usaf_station not in metadata:
              metadata[usaf_station] = {"usaf_id": usaf_station, "years": {}}
          metadata[usaf_station]["years"][year] = [
              {
                  "wban_id": row.WBAN,
                  "counts": [
                      row.JAN,
                      row.FEB,
                      row.MAR,
                      row.APR,
                      row.MAY,
                      row.JUN,
                      row.JUL,
                      row.AUG,
                      row.SEP,
                      row.OCT,
                      row.NOV,
                      row.DEC,
                  ],
              }
              for i, row in group.iterrows()
          ]
      return metadata