Function read_digraph 

pub fn read_digraph<N, E, P>(
    path: P,
    format: GraphFormat,
    weighted: bool,
) -> Result<DiGraph<N, E>>
where
    N: Node + Debug + FromStr + Clone,
    E: EdgeWeight + Copy + Debug + Default + FromStr,
    P: AsRef<Path>,

Reads a directed graph from a file

Arguments

• path - Path to the file
• format - Format of the file
• weighted - Whether the graph has edge weights

Returns

• Ok(DiGraph) - The directed graph read from the file
• Err(GraphError) - If there was an error reading the file