feat: Make CompiledGraph displayable in Juypyter with display() (#2159)

libs/langgraph/langgraph/graph/graph.py

@@ -628,3 +628,11 @@ class CompiledGraph(Pregel):
                     add_edge(key, end, conditional=True)
 
         return graph
+
+    def _repr_mimebundle_(self, **kwargs) -> dict[str, Any]:
+        """Mime bundle used by Jupyter to display the graph"""
+        output = {
+            "text/plain": repr(self),
+            "image/png": self.get_graph().draw_mermaid_png()
+        }
+        return output