Add back in root().

src/lib.rs

@@ -49,6 +49,12 @@ impl DiagnosticGraph {
         }
     }
 
+    /// Get the root key.
+    /// Needed to do searches in the graph outside of this crate.
+    pub fn root(&self) -> limbo_graph::Key {
+        self.graph.root_key()
+    }
+
     /// Get the value of a specific element of the graph.
     /// Will error if the key is not in the graph, or if the key
     /// is the root, which doesn't have a value.