docs: def _find_sink_scc(self):
          """
          Set self._sink_scc_labels, which is a list containing the labels of
          the strongly connected components.
  
          """
          condensation_lil = self._condensation_lil()
  
          # A sink SCC is a SCC such that none of its members is strongly
          # connected to nodes in other SCCs
          # Those k's such that graph_condensed_lil.rows[k] == []
          self._sink_scc_labels = \
              np.where(np.logical_not(condensation_lil.rows))[0]