docs: def get_mapping_registry(content_type):
      """
      Returns the data element registry for the given content type (a Singleton).
  
      :Note: This only works after a representer for the given content type
          has been created.
      """
      reg = get_current_registry()
      rpr_reg = reg.queryUtility(IRepresenterRegistry)
      return rpr_reg.get_mapping_registry(content_type)