pub fn vertices_without_successors(&self) -> Vec<&V> {
        self.vertices
            .values()
            .filter(|v| self.successors.get(&v.index()).unwrap().is_empty())
            .collect()
    }
/// Returns all vertices which don't have any successors in the graph.
Returns all vertices which don't have any successors in the graph.
Returns all vertices which don ' t have any successors in the graph .
pub fn vertices_without_successors(&self) -> Vec<&V> {
        self.vertices
            .values()
            .filter(|v| self.successors.get(&v.index()).unwrap().is_empty())
            .collect()
    }
pub fn vertices_without_successors ( & self ) -> Vec < & V > { self . vertices . values ( ) . filter ( | v | self . successors . get ( & v . index ( ) ) . unwrap ( ) . is_empty ( ) ) . collect ( ) }
Returns all vertices which don't have any successors in the graph.
Returns all vertices which don ' t have any successors in the graph .
&self
&self