def METHOD_NAME(self, signature_a=True, signature_b=True) -> bytes:
    """
    Encode this block for transport.
    :param signature_a: False to pack EMPTY_SIG in the location of signature A, true to pack the signature A field.
    :param signature_b: False to pack EMPTY_SIG in the location of signature B, true to pack the signature B field.
    :return: bytes object the data was packed into.
    """
    args = [self.sequence_number, self.public_key_a, self.public_key_b,
            self.signature_a if signature_a else EMPTY_SIGNATURE,
            self.signature_b if signature_b else EMPTY_SIGNATURE, self.amount, self.timestamp]
    return default_serializer.pack_serializable(BandwidthTransactionPayload(*args, 0))