code: def suppress_deg_one_node(self, to_par_edge, nd_id, to_child_edge):
          
          # circumvent the node with nd_id
          to_child_edge_id = to_child_edge['@id']
          par = to_par_edge['@source']
          self._edge_by_source[par][to_child_edge_id] = to_child_edge
          to_child_edge['@source'] = par
          # make it a tip...
          del self._edge_by_source[nd_id]
          # delete it
          self._del_tip(nd_id)
docs: Deletes to_par_edge and nd_id. To be used when nd_id is an out-degree= 1 node