def serialize(self, with_witness=True):
    r = b''
    r += ser_uint256(self.blockhash)
    if with_witness:
        r += ser_vector(self.transactions, 'serialize_with_witness')
    else:
        r += ser_vector(self.transactions, 'serialize_without_witness')
    return r
def serialize(self, with_witness=True):
    r = b
    r += ser_uint256(self.blockhash)
    if with_witness:
        r += ser_vector(self.transactions, 'serialize_with_witness')
    else:
        r += ser_vector(self.transactions, 'serialize_without_witness')
    return r