docs: def path_to_url(self, path):
          """Build URL from a path.
  
          :param path: relative path of the schema.
          :returns: The schema complete URL or ``None`` if not found.
          """
          if path not in self.schemas:
              return None
          return self.url_map.bind(
              self.app.config['JSONSCHEMAS_HOST'],
              url_scheme=self.app.config['JSONSCHEMAS_URL_SCHEME']
          ).build(
              'schema', values={'path': path}, force_external=True)