def delegates():
        """returns a list of named tuples of all delegates.
        {username: {'pubkey':pubkey, 'timestamp':timestamp, 'address':address}}"""
        qry = DbCursor().execute_and_fetchall("""
            SELECT delegates."username", delegates."transactionId", transactions."timestamp", transactions."senderId", 
            transactions."senderPublicKey" 
            FROM transactions
            JOIN delegates ON transactions."id" = delegates."transactionId"
        """)

        Delegate = namedtuple(
            'delegate',
            'username pubkey timestamp address transactionId')
        res = []
        for i in qry:
            registration = Delegate(
                username=i[0],
                pubkey=binascii.hexlify(i[4]).decode("utf-8"),
                timestamp=i[2],
                address=i[3],
                transactionId=i[1]
            )
            res.append(registration)
        return res
returns a list of named tuples of all delegates.
        {username: {'pubkey':pubkey, 'timestamp':timestamp, 'address':address}}