def to_signed(cls, type_):
        """ Return signed type or equivalent
        """
        if type_ in cls.unsigned:
            return {TYPE.ubyte: TYPE.byte_,
                    TYPE.uinteger: TYPE.integer,
                    TYPE.ulong: TYPE.long_}[type_]
        if type_ in cls.decimals or type_ in cls.signed:
            return type_
        return cls.unknown
Return signed type or equivalent