Why does MATE not allow extracting the same the field twice?

edit

Hello, guys.

mate file like

Pdu sip_pdu Proto sip Transport udp/ip {
  Extract id From sip.Call-ID;
  Extract callid From sip.Call-ID;
};

will alert on wireshark startup that "fieald already added as 'id' ".

Why I can Extract some field only once? Are there some way/hack to Extract it twice?