code: def Filter(self, filename_spec):
      
      if "@" in filename_spec:
        file_path, package_name = filename_spec.split("@")
      else:
        file_path, package_name = filename_spec, Resource.default_package
  
      resource_path = package.ResourcePath(package_name, file_path)
      if resource_path is not None:
        return resource_path
  
  
      # pylint: disable=unreachable
      raise FilterError(
          "Unable to find resource %s while interpolating: " % filename_spec)
docs: Use pkg_resources to find the path to the required resource.