blacken api_core and core (#6668)

* blacken api_core and core
diff --git a/.flake8 b/.flake8
index 3db9b73..3da787c 100644
--- a/.flake8
+++ b/.flake8
@@ -3,6 +3,7 @@
 # Note: this forces all google imports to be in the third group. See
 # https://github.com/PyCQA/flake8-import-order/issues/111
 application-import-names=google
+ignore = E203, E266, E501, W503
 exclude =
   __pycache__,
   .git,