black updated and rerun

Author: rmorshea

.pre-commit-config.yaml

@@ -1,6 +1,6 @@
 repos:
   - repo: https://github.com/ambv/black
-    rev: 20.8b1
+    rev: 21.12b0
     hooks:
       - id: black
   - repo: https://github.com/PyCQA/flake8

src/idom/core/layout.py

@@ -705,7 +705,6 @@ def _process_child_type_and_key(
     def _default_key(index: int) -> Any:  # pragma: no cover
         return index
 
-
 else:
 
     def _default_key(index: int) -> Any: