docs: 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')