def to_wire(self, file, compress=None, origin=None):
    header = struct.pack('!BBB', self.usage, self.selector, self.mtype)
    file.write(header)
    file.write(self.cert)
def to_wire(self, file, compress=None, origin=None):
    header = struct.pack('!BBB', self.usage, self.selector, self.mtype)
    file.write(header)
    file.write(self.cert)