docs: def deep_update(source, overrides):
      """Update a nested dictionary or similar mapping.
  
      Modify ``source`` in place.
  
      :type source: collections.Mapping
      :type overrides: collections.Mapping
      :rtype: collections.Mapping
      """
      for key, value in overrides.items():
          if isinstance(value, collections.Mapping) and value:
              returned = deep_update(source.get(key, {}), value)
              source[key] = returned
          else:
              source[key] = overrides[key]
      return source