wrong type for Rational in DNGTags

[SuTanTank]

class DNGTags:
    def __init__(self):
        self.__tags__ = dict()

    def set(self, tag, value):
        if isinstance(value, int):
            self.__tags__[tag] = (value,)
        elif isinstance(value, float):
            self.__tags__[tag] = (value,)
        elif isinstance(value, str):
            self.__tags__[tag] = value
        elif len(value) > 1:
            self.__tags__[tag] = value
        else:
            self.__tags__[tag] = (value,)

    def get(self, tag):
        return self.__tags__[tag]

    def list(self):
        l = list()
        for k, v in self.__tags__.items():
            l.append((k, v))
        return l

def setValue(self, value):
        if   self.DataType == Type.Byte:      self.Value = struct.pack('<%sB' % len(value), *value)
        ...
        elif self.DataType == Type.Rational:
            self.Value = struct.pack('<%sL' % (len(value)*2), *[item for sublist in value for item in sublist])

When the input value is a single rational number, what's is the acceptable value to be set?

As setValue() defined, value should be a 2D array, like [[a, b]], but DNGTags.set() will convert single element list to tuple.