Given a subdomain record, get its neighbors.
        I.e. get all of the subdomain records with the previous sequence number,
        and get all of the subdomain records with the next sequence number
        Returns {'prev': [...blockchain order...], 'cur': [...blockchain order...], 'fut': [...blockchain order...]}

def get_subdomain_history_neighbors(self, cursor, subdomain_rec):
        """
        Given a subdomain record, get its neighbors.
        I.e. get all of the subdomain records with the previous sequence number,
        and get all of the subdomain records with the next sequence number
        Returns {'prev': [...blockchain order...], 'cur': [...blockchain order...], 'fut': [...blockchain order...]}
        """
        # what's the subdomain's immediate prior history?
        hist = self.subdomain_db.get_subdomain_history(subdomain_rec.get_fqn(), include_unaccepted=True, start_sequence=subdomain_rec.n-1, end_sequence=subdomain_rec.n, cur=cursor)
        hist.sort(lambda h1, h2: -1 if h1.n < h2.n or (h1.n == h2.n and h1.parent_zonefile_index < h2.parent_zonefile_index) \
                                 else 0 if h1.n == h2.n and h1.parent_zonefile_index == h2.parent_zonefile_index \
                                 else 1)

        # what's the subdomain's current and immediate future?
        fut = self.subdomain_db.get_subdomain_history(subdomain_rec.get_fqn(), include_unaccepted=True, start_sequence=subdomain_rec.n, end_sequence=subdomain_rec.n+2, cur=cursor)
        fut.sort(lambda h1, h2: -1 if h1.n < h2.n or (h1.n == h2.n and h1.parent_zonefile_index < h2.parent_zonefile_index) \
                                 else 0 if h1.n == h2.n and h1.parent_zonefile_index == h2.parent_zonefile_index \
                                 else 1)

        # extract the current (conflicting) records from the future
        cur = []
        tmp_fut = []
        for f in fut:
            if f.n == subdomain_rec.n:
                cur.append(f)
            else:
                tmp_fut.append(f)

        fut = tmp_fut

        ret = {'prev': hist, 'cur': cur, 'fut': fut}
        return ret