You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mysql_federated.rs
    path of file: ./repos/databend/src/query/service/tests/it/servers/mysql
    
    the code of the file until where you have to start completion: // Copyright 2022 Datafuse Labs.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use databend_common_exception::Result;
use databend_common_
    
fn test_mysql_federated() -> Result<()> {
    let federated = MySQLFederated::create();

    //
    {
        let query = "select 1";
        let result = federated.check(query);
        assert!(result.is_none());
    }

    // variables
    {
        let query = "select @@tx_isolation, @@session.tx_isolation";
        let result = federated.check(query);
        assert!(result.is_some());

        if let Some((_, block)) = result {
            let expect = vec![
                "+-------------------+-------------------+",
                "| Column 0          | Column 1          |",
                "+-------------------+-------------------+",
                "| 'REPEATABLE-READ' | 'REPEATABLE-READ' |",
                "+-------------------+-------------------+",
            ];

            assert_blocks_eq(expect, &[block]);
        }
    }

    // complex variables
    {
        let query = "/* mysql-connector-java-8.0.17 (Revision: 16a712ddb3f826a1933ab42b0039f7fb9eebc6ec) */SELECT  @@session.auto_increment_increment AS auto_increment_increment, @@character_set_client AS character_set_client, @@character_set_connection AS character_set_connection, @@character_set_results AS character_set_results, @@character_set_server AS character_set_server, @@collation_server AS collation_server, @@collation_connection AS collation_connection, @@init_connect AS init_connect, @@interactive_timeout AS interactive_timeout, @@license AS license, @@lower_case_table_names AS lower_case_table_names, @@max_allowed_packet AS max_allowed_packet, @@net_write_timeout AS net_write_timeout, @@performance_schema AS performance_schema, @@sql_mode AS sql_mode, @@system_time_zone AS system_time_zone, @@time_zone AS time_zone, @@transaction_isolation AS transaction_isolation, @@wait_timeout AS wait_timeout;";
        let result = federated.check(query);
        assert!(result.is_some());

        if let Some((_, block)) = result {
            let expect = vec![
                "+----------+----------+----------+----------+----------+----------+----------+----------+------------+----------+-----------+-------------+------------+-----------+-----------+-----------+-----------+-------------------+------------+",
                "| Column 0 | Column 1 | Column 2 | Column 3 | Column 4 | Column 5 | Column 6 | Column 7 | Column 8   | Column 9 | Column 10 | Column 11   | Column 12  | Column 13 | Column 14 | Column 15 | Column 16 | Column 17         | Column 18  |",
                "+----------+----------+----------+----------+----------+----------+----------+----------+------------+----------+-----------+-------------+------------+-----------+-----------+-----------+-----------+-------------------+------------+",
                "| '0'      | '0'      | '0'      | '0'      | '0'      | '0'      | '0'      | '0'      | '31536000' | '0'      | '0'       | '134217728' | '31536000' | '0'       | '0'       | 'UTC'     | 'UTC'     | 'REPEATABLE-READ' | '31536000' |",
                "+----------+----------+----------+----------+----------+----------+----------+----------+------------+----------+-----------+-------------+------------+-----------+-----------+-----------+-----------+-------------------+------------+",
            ];

            assert_blocks_eq(expect, &[block]);
        }
    }

    Ok(())
}