def good_signatures(self):
        """
        A generator yielding namedtuples of all signatures that were successfully verified
        in the operation that returned this instance. The namedtuple has the following attributes:

        ``sigsubj.verified`` - ``bool`` of whether the signature verified successfully or not.

        ``sigsubj.by`` - the :py:obj:`~pgpy.PGPKey` that was used in this verify operation.

        ``sigsubj.signature`` - the :py:obj:`~pgpy.PGPSignature` that was verified.

        ``sigsubj.subject`` - the subject that was verified using the signature.
        """
        for s in [ i for i in self._subjects if i.verified ]:
            yield s