Run a function as `selected` for iron-pages

In this issue I saw a very interesting use of iron-pages:

<carbon-route route="[[route]]" patte="/groups" active="{{isAll}}">
</carbon-route>
<carbon-route route="[[route]]" patte="/groups/:groupId" active="{{isProfile}}"></carbon-route>
<carbon-route route="[[route]]" patte="/groups/:groupId/members" active="{{isMembers}}"></carbon-route>

<iron-pages attr-for-selected="key" selected="getKey(isAll, isProfile, isMember)">
  <div key="all">...</div>
  <div key="profile">...</div>
  <div key="members">...</div>
</iron-pages>
...

/** Map the various flags for the `selected` property of iron-pages: */
getKey: function(isAll, isProfile, isMembers) {
  // Workaround for issue #61: match most specific first
  if (isMembers) retu 'members';
  if (isProfile) retu 'profile';
  if (isAll) retu 'all';
  retu 'default';
}

Doing selected="getKey(isAll, isProfile, isMember)"> would be awesome! But... I haven't managed to find any doc on data binding about it.

Is this even supported?

Merc.