expression#expr_2 = '(4 + 2) * 3'
   expression#expr_bracket = '(4 + 2)'
      SYMBOL_LB = '('
      expression#expr_3 = '4 + 2'
         expression#expr_number = '4'
            number$1 = '4'
               numberInt$1 = '4'
                  NUMBER_INT = '4'
         operator3$1 = '+'
            operatorAdd$1 = '+'
               SYMBOL_ADD = '+'
         expression#expr_number = '2'
            number$1 = '2'
               numberInt$1 = '2'
                  NUMBER_INT = '2'
      SYMBOL_RB = ')'
   operator2#opmul = '*'
      operatorMul$1 = '*'
         SYMBOL_MUL = '*'
   expression#expr_number = '3'
      number$1 = '3'
         numberInt$1 = '3'
            NUMBER_INT = '3'
