@property
def value(self):
    val = self._operands[0].value
    l = len(self._operands)
    i = 1
    while (i < l):
        val = self.solve(val, self._operands[i].value)
        i += 1
    return val
@property
def value(self):
    val = self._operands[0].value
    l = len(self._operands)
    i = 1
    while (i < l):
        val = self.solve(val, self._operands[i].value)
        i += 1
    return val