<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _find_new_additions(self):
 """Find any nodes in the graph that need to be added to the internal queue and add them. Callers must hold the lock. """

        for node, in_degree in self.graph.in_degree_iter():
            if not self._already_known(node) and in_degree == 0:
                self.inner.put((self._scores[node], node))
                self.queued.add(node)