To retrieve collections with informations about Jingle call events item-type
attribute needs to be added to <list/>
element from section 7.1 Retrieving a List of Collections of XEP-0136 specification with value set to call
.
A result it will be returned as specified in XEP-0136, but <list/>
element will contain <events/>
element for each collections instead of <chat/>
element.
Additionally <list/>
element will have item-type
attribute set to call
.