def make_grpc_unary_method(channel, service_name, method_descriptor,
    symbol_database_instance):
    """Make grp callable on the channel.

    Args:
        channel: grpc channel
        service_name: name of service
        method_descriptor: method descriptor
        symbol_database_instance: symbol db instance
    """
    input_prototype = symbol_database_instance.GetPrototype(method_descriptor
        .input_type)
    output_prototype = symbol_database_instance.GetPrototype(method_descriptor
        .output_type)
    method = channel.unary_unary('/{}/{}'.format(service_name,
        method_descriptor.name), request_serializer=input_prototype.
        SerializeToString, response_deserializer=output_prototype.FromString)
    return method
