Add an API helper to link two elements

Closes #277 (closed)

tests/test_elements_worker/test_elements.py

@@ -1246,19 +1246,19 @@ def test_create_elements_integrity_error(
     [
         (
             {"parent": None, "child": None},
-            "parent shouldn't be null and should be of type Element or CachedElement",
+            "parent shouldn't be null and should be of type Element",
         ),
         (
             {"parent": "not an element", "child": None},
-            "parent shouldn't be null and should be of type Element or CachedElement",
+            "parent shouldn't be null and should be of type Element",
         ),
         (
             {"parent": Element(zone=None), "child": None},
-            "child shouldn't be null and should be of type Element or CachedElement",
+            "child shouldn't be null and should be of type Element",
         ),
         (
             {"parent": Element(zone=None), "child": "not an element"},
-            "child shouldn't be null and should be of type Element or CachedElement",
+            "child shouldn't be null and should be of type Element",
         ),
     ],
 )