@Test
public void testParserMatrixSum() {

    Expr expr1 = Parser.parseExpr("sum(http_requests_total{method=\"get\"})");
    System.out.println(expr1.toString());
    Expr expr = Parser.parseExpr("sum_over_time(http_requests_total{method=\"get\"}[5m])");
    System.out.println(expr.toString());
}