pub trait GraphLog<K: Clone + Eq + Hash> {
// Required methods
fn add_node(
&mut self,
id: &K,
edges: &[Edge<K>],
node_symbol: &str,
text: &str
) -> Result<()>;
fn default_node_symbol(&self) -> &str;
fn width(&self, id: &K, edges: &[Edge<K>]) -> usize;
}