How to use the pgpy.decorators.sdproperty function in PGPy

    @sdproperty
    def amount(self):
        return self._amount

    @sdproperty
    def sigtype(self):
        return self._sigtype

    @sdproperty
    def regex(self):
        return self._regex

    @sdproperty
    def bflag(self):
        return self._bool

    @sdproperty
    def version(self):
        return self._version

    @sdproperty
    def signer(self):
        return self._signer

    @sdproperty
    def created(self):
        return self._created

    @sdproperty
    def fingerprint(self):
        return self._fingerprint

    @sdproperty
    def llen(self):
        l = self.length
        lf = self._lenfmt

        if lf == 1:
            # new-format length
            if 192 > l:
                return 1

            elif 8384 > self.length:  # >= 192 is implied
                return 2

            else:
                return 5

        else:

    @sdproperty
    def image(self):
        return self._image