pub trait GrowableGraphTrait<NodeId, EdgeId> {
// Required methods
fn get_source_index(&self, edge_index: &EdgeId) -> Option<NodeId>;
fn get_target_index(&self, edge_index: &EdgeId) -> Option<NodeId>;
fn nodes_len(&self) -> usize;
fn edges_len(&self) -> usize;
fn get_nodes_ids(&self) -> Vec<NodeId>;
}