def _find_scc(self):
        """
        Set ``self._num_scc`` and ``self._scc_proj``
        by calling ``scipy.sparse.csgraph.connected_components``:
        * docs.scipy.org/doc/scipy/reference/sparse.csgraph.html
        * github.com/scipy/scipy/blob/master/scipy/sparse/csgraph/_traversal.pyx

        ``self._scc_proj`` is a list of length `n` that assigns to each node
        the label of the strongly connected component to which it belongs.

        """
        # Find the strongly connected components
        self._num_scc, self._scc_proj = \
            csgraph.connected_components(self.csgraph, connection='strong')