//so the user does not have to do it, the implemented hack avoids another
//colon to be added in case there already is one
@Override
public void completeQNameRef_Prefix(EObject model, Assignment assignment,
ContentAssistContext context, final ICompletionProposalAcceptor acceptor) {
ICompletionProposalAcceptor colonAddingAcceptor=acceptor;
if(!context.getCurrentNode().getText().contains(":")){
colonAddingAcceptor=new ColonAddingAcceptor(acceptor);
}
super.completeQNameRef_Prefix(model, assignment, context, colonAddingAcceptor);
}