fix(graph): sorts keys to make serialization determistic

Fixes #183

Author: jordimas

src/langchain_google_spanner/graph_store.py

@@ -961,19 +961,19 @@ def __repr__(self) -> str:
                             "property name": name,
                             "property type": properties[name],
                         }
-                        for name in self.labels[label].prop_names
+                        for name in sorted(self.labels[label].prop_names)
                     ]
-                    for label in node_labels
+                    for label in sorted(node_labels)
                 },
                 "Edge properties per edge label": {
                     label: [
                         {
                             "property name": name,
                             "property type": properties[name],
                         }
-                        for name in self.labels[label].prop_names
+                        for name in sorted(self.labels[label].prop_names)
                     ]
-                    for label in edge_labels
+                    for label in sorted(edge_labels)
                 },
                 "Possible edges per label": {
                     label: [