private Set<SubCommand> subscribe(final FrameworkAgent<?> agent, final Map<String, Type> symbols) {
final Set<SubCommand> newSubs = new HashSet<SubCommand>();
for (final Entry<String, SubCommand.Type> e : symbols.entrySet()) {
final SubCommand sub = subscribe(agent, e.getKey(), e.getValue());
if (!sub.isNull()) {
newSubs.add(sub);
}
}
return newSubs;