Function reverse_graph 

pub fn reverse_graph<N, ID, E>(
    input: impl Iterator<Item = Result<(N, Vec<GraphEdge<ID>>), E>>,
    as_id: impl Fn(&N) -> &ID,
) -> Result<Vec<(N, Vec<GraphEdge<ID>>)>, E>
where
    ID: Clone + Eq + Hash,

Creates new graph in which nodes and edges are reversed.