adjust yapf config temporarily because of yapf issue #1164

.pre-commit-config.yaml

@@ -4,6 +4,7 @@ repos:
     hooks:
     - id: yapf
       args: ['--in-place', '--recursive', '--style', 'google']
+      require_serial: true
 
 -   repo: https://github.com/PyCQA/docformatter    # To format the doc strings to conform PEP257
     rev: v1.7.5