def METHOD_NAME(user, query_server=None):
  if query_server is None:
    query_server = get_query_server_config()
  if query_server['server_name'] == 'mysql':
    from librdbms.server.mysql_lib import MySQLClient
    return Rdbms(MySQLClient(query_server, user), MYSQL)
  elif query_server['server_name'] in ('postgresql', 'postgresql_psycopg2'):
    from librdbms.server.postgresql_lib import PostgreSQLClient
    return Rdbms(PostgreSQLClient(query_server, user), POSTGRESQL)
  elif query_server['server_name'] in ('sqlite', 'sqlite3'):
    from librdbms.server.sqlite_lib import SQLiteClient
    return Rdbms(SQLiteClient(query_server, user), SQLITE)
  elif query_server['server_name'] == 'oracle':
    from librdbms.server.oracle_lib import OracleClient
    return Rdbms(OracleClient(query_server, user), ORACLE)