Get claims holding extra identity info from the claims set.

        Returns a dictionary of extra claims or None if there are none.

        :param claims_set: set of claims, which was included in the received
        token.

def get_extra_claims(self, claims_set):
        """Get claims holding extra identity info from the claims set.

        Returns a dictionary of extra claims or None if there are none.

        :param claims_set: set of claims, which was included in the received
        token.
        """
        reserved_claims = (
            self.userid_claim, "iss", "aud", "exp", "nbf", "iat", "jti",
            "refresh_until", "nonce"
        )
        extra_claims = {}
        for claim in claims_set:
            if claim not in reserved_claims:
                extra_claims[claim] = claims_set[claim]
        if not extra_claims:
            return None

        return extra_claims