def get_all_thread_participants(exploration_id, thread_id):
 return set([m.author_id for m in get_messages(exploration_id, thread_id) if user_services.is_user_registered(m.author_id)])

def get_all_thread_participants ( exploration_id , thread_id ) : return set ( [ m . author_id for m in get_messages ( exploration_id , thread_id ) if user_services . is_user_registered ( m . author_id ) ] )
fetches all participants of the given thread .