Get the set of names owned by a particular script-pubkey.

def get_names_owned_by_sender( self, sender_pubkey, lastblock=None ):
        """
        Get the set of names owned by a particular script-pubkey.
        """
        cur = self.db.cursor()
        if lastblock is None:
            lastblock = self.lastblock 

        names = namedb_get_names_by_sender( cur, sender_pubkey, lastblock )
        return names