container can deal with itself:w

tfields/core.py

@@ -2520,13 +2520,16 @@ class Container(AbstractNdarray):
         >>> sphere2 = sphere.copy() * 3
         >>> c = tfields.Container([sphere, sphere2])
 
-        # >>> c.save("~/tmp/spheres.npz")
-        # >>> c1 = tfields.Container.load("~/tmp/spheres.npz")
+        >>> c.save("~/tmp/spheres.npz")
+        >>> c1 = tfields.Container.load("~/tmp/spheres.npz")
     """
 
     __slots__ = ["items", "labels"]
 
     def __new__(cls, items, **kwargs):
+        if issubclass(type(items), cls):
+            items = items.items
+            kwargs.setdefault(items.labels)
         kwargs["items"] = items
         cls._update_slot_kwargs(kwargs)
 
@@ -2544,6 +2547,13 @@ class Container(AbstractNdarray):
         return obj
 
 
+class Maps(Container):
+    def __new__(cls, items, **kwargs):
+        if not issubclass(type(items), cls):
+            print("ASDF")
+        super().__new__(items, **kwargs)
+
+
 if __name__ == "__main__":  # pragma: no cover
     import doctest
     doctest.testmod()