@classmethod
def one(cls):
    """
        Return the field's neutral element of multiplication (one).

        One (or unity) in a FractionField is a fraction @f$ rac{1}{1} @f$,
        where @f$ 1 @f$ denotes the one of the underlying integral domain.
        """
    return cls(cls._integral_domain.one(), cls._integral_domain.one())
