DynamicMessage message = (DynamicMessage)iterator.next();
Object item = fromProtoValue(item_field, message.getField(item_field));
Boolean exists = (Boolean)message.getField(exists_field);
if (exists) {
set = (ITransientSet)set.conj(item);
} else {
try {
set = set.disjoin(item);
} catch (Exception e) {
e.printStackTrace();