code: def _get_cached_path(
              self,
              field_name,
              path_or_url,
              download_if_missing=False,
              overwrite=False):
          
          if len(field_name) == 0:
              raise ValueError("Expected non-empty field name")
          if len(path_or_url) == 0:
              raise ValueError("Expected non-empty path_or_url")
          return self.download_cache.local_path_or_install_error(
              field_name=field_name,
              path_or_url=path_or_url,
              download_if_missing=download_if_missing,
              overwrite=overwrite)
docs: Get the local path for a possibly remote file, invoking either
          a download or install error message if it's missing.