code: def add_handler(self, f):
          
          if f.__name__.startswith('rpc_'):
              raise ValueError("Server method names cannot start with rpc_.")
          self._json_rpc_methods[f.__name__] = f
          return f
docs: Adds the function f to a dictionary of JSON RPC methods.
  
          :param callable f: Method to be exposed
          :return: