{"ast_node_type":"variable","tokens":[{"end":54,"kind":"keyword","start":0,"text":"let"}]}
        let (row1_start, row1_end) = self.range(row1);
        assert!(row1.index() < self.num_rows && row2.index() < self.num_rows);
        let (row2_start, row2_end) = self.range(row2);