create submodule design pattern

nib/std/default.nix

@@ -1,4 +1,12 @@
-builtins.listToAttrs [
-  (import ./attrs.nix)
-  (import ./lists.nix)
-]
+{}: let
+  attrs = import ./attrs.nix {inherit lists;};
+  lists = import ./lists.nix {};
+  result = import ./lists.nix {inherit lists;};
+in
+  builtins.listToAttrs [
+    # submodule is included directly to this module (ie self.myFunc)
+
+    # submodule content is accessible first by submodule name
+    # then by the name of the content (ie self.submodule.myFunc)
+    {inherit attrs lists result;}
+  ]