def extract_add_server(pb2_grpc):
    """
    Extract add to server function from pb2_grpc module
    :param pb2_grpc:
    :return: function for add_to_server
    :type: function
    """
    members = dir(pb2_grpc)
    for name in members:
        if name.startswith('add_') and name.endswith('_to_server'):
            _add_to_server = getattr(pb2_grpc, name)
            return _add_to_server
    return None
