new_contents: import os
  
  # Directory that the project lives in, aka ../..
  SITE_ROOT = '/'.join(os.path.dirname(__file__).split('/')[0:-2])
  
  TEMPLATE_DIRS = (
      "%s/templates/" % SITE_ROOT, # Your custom template directory, before the RTD one to override it.
      "%s/readthedocs/templates/" % SITE_ROOT, # Default RTD template dir
  )
  
subject: Add RTD local_settings file, to add custom templates.