pub fn vertex_get_incident_edge(&self, vertex_id: Option<VertexIndex>) -> Option<EdgeIndex> {
        let _ = vertex_id?;
        self.vertex_get_(vertex_id)
            .and_then(|x| x.get().incident_edge_)
    }
/// return one of the edges originating at the vertex
return one of the edges originating at the vertex
return one of the edges originating at the vertex
pub fn vertex_get_incident_edge(&self, vertex_id: Option<VertexIndex>) -> Option<EdgeIndex> {
        let _ = vertex_id?;
        self.vertex_get_(vertex_id)
            .and_then(|x| x.get().incident_edge_)
    }
pub fn vertex_get_incident_edge ( & self , vertex_id : Option < VertexIndex > ) -> Option < EdgeIndex > { let _ = vertex_id ? ; self . vertex_get_ ( vertex_id ) . and_then ( | x | x . get ( ) . incident_edge_ ) }
return one of the edges originating at the vertex
return one of the edges originating at the vertex
&self
vertex_id
Option<VertexIndex>