code: def _finalized(self):
          
          return \
              len(self._finalized_dependencies) >= self.dependency_count \
              and len(self._enqueued_dependencies) >= self.dependency_count
docs: Return true if all dependencies have informed this node that they'll
          be sending no more data (by calling _finalize()), and that they have
          sent at least one batch of data (by calling enqueue())