Postgres: [USING method] does not support index creation.

[step-baby]

#[test]
fn test_create_index() {
     let pg_dialect = PostgreSqlDialect {};
     let sql = r#"
     CREATE INDEX "test_indexes" ON "public"."test" USING btree ("id","user_id","action","result");"#;
     let mut ast = Parser::parse_sql(&pg_dialect, sql).unwrap();
}

The result after the test case is executed：

called `Result::unwrap()` on an `Err` value: ParserError("Expected (, found: USING")
thread 'ast::tests::test_create_index' panicked at 'called `Result::unwrap()` on an `Err` value: ParserError("Expected (, found: USING")',