def serialize(self):
    r = b''
    r += struct.pack('<B', self.filter_type)
    r += struct.pack('<I', self.start_height)
    r += ser_uint256(self.stop_hash)
    return r
def serialize(self):
    r = b
    r += struct.pack('<B', self.filter_type)
    r += struct.pack('<I', self.start_height)
    r += ser_uint256(self.stop_hash)
    return r