code: def get_template_sources(self, template_name, template_dirs=None):
          
          if ':' not in template_name:
              return []
          app_name, template_name = template_name.split(":", 1)
          template_dir = get_app_template_dir(app_name)
          if template_dir:
              return [get_template_path(template_dir, template_name, self)]
          return []
docs: Return the absolute paths to "template_name" in the specified app
          If the name does not contain an app name (no colon), an empty list
          is returned.
          The parent FilesystemLoader.load_template_source() will take care
          of the actual loading for us.