We need to select the correct one on dissection. We use the length for
    that, as 1 for client version would emply an empty list.

def _TLS_Ext_CertTypeDispatcher(m, *args, **kargs):
    """
    We need to select the correct one on dissection. We use the length for
    that, as 1 for client version would emply an empty list.
    """
    tmp_len = struct.unpack("!H", m[2:4])[0]
    if tmp_len == 1:
        cls = TLS_Ext_ServerCertType
    else:
        cls = TLS_Ext_ClientCertType
    return cls(m, *args, **kargs)