Saving dtypes as metadata for roundtrip consistency

src/tracksdata/graph/_base_graph.py

@@ -1282,7 +1282,6 @@ def from_other(cls: type[T], other: "BaseGraph", **kwargs) -> T:
         current_edge_attr_schemas = graph._edge_attr_schemas()
         for k, v in other._edge_attr_schemas().items():
             if k not in current_edge_attr_schemas:
-                print(f"Adding edge attribute key: {k} with dtype: {v.dtype} and default value: {v.default_value}")
                 graph.add_edge_attr_key(k, v.dtype, v.default_value)
 
         edge_attrs = edge_attrs.with_columns(
@@ -1927,13 +1926,6 @@ def _private_metadata(self) -> MetadataView:
             is_public=False,
         )
 
-    def _private_metadata_for_copy(self) -> dict[str, Any]:
-        """
-        Return private metadata entries that should be propagated by `from_other` or `to_geff`.
-        Backends can override this to exclude backend-specific private metadata.
-        """
-        return dict(self._private_metadata)
-
     @classmethod
     def _is_private_metadata_key(cls, key: str) -> bool:
         return key.startswith(cls._PRIVATE_METADATA_PREFIX)
@@ -1962,6 +1954,14 @@ def _remove_metadata_with_validation(self, key: str, *, is_public: bool = True)
         self._validate_metadata_key(key, is_public=is_public)
         self._remove_metadata(key)
 
+    def _private_metadata_for_copy(self) -> dict[str, Any]:
+        """
+        Return private metadata entries that should be propagated by `from_other`.
+
+        Backends can override this to exclude backend-specific private metadata.
+        """
+        return dict(self._private_metadata)
+
     @abc.abstractmethod
     def _metadata(self) -> dict[str, Any]:
         """

src/tracksdata/graph/_rustworkx_graph.py

@@ -343,7 +343,7 @@ def __init__(self, rx_graph: rx.PyDiGraph | None = None) -> None:
         self._time_to_nodes: dict[int, list[int]] = {}
         self.__node_attr_schemas: dict[str, AttrSchema] = {}
         self.__edge_attr_schemas: dict[str, AttrSchema] = {}
-        self._overlaps: list[list[int, 2]] = []
+        self._overlaps: list[list[int]] = []
 
         # Add default node attributes with inferred schemas
         self.__node_attr_schemas[DEFAULT_ATTR_KEYS.T] = AttrSchema(
@@ -1159,16 +1159,11 @@ def edge_attrs(
 
         edge_map = rx_graph.edge_index_map()
         if len(edge_map) == 0:
-            return pl.DataFrame(
-                {
-                    key: []
-                    for key in [
-                        *attr_keys,
-                        DEFAULT_ATTR_KEYS.EDGE_SOURCE,
-                        DEFAULT_ATTR_KEYS.EDGE_TARGET,
-                    ]
-                }
-            )
+            empty_columns = {}
+            for key in [*attr_keys, DEFAULT_ATTR_KEYS.EDGE_SOURCE, DEFAULT_ATTR_KEYS.EDGE_TARGET]:
+                schema = self._edge_attr_schemas()[key]
+                empty_columns[key] = pl.Series(name=key, values=[], dtype=schema.dtype)
+            return pl.DataFrame(empty_columns)
 
         source, target, data = zip(*edge_map.values(), strict=False)