docs: def get_nested_dicts(nested_dict, *keys, default=None, init_nesting=dict):
      """
      Get/Initialize the value of nested-dictionaries.
  
      :param nested_dict:
          Nested dictionary.
      :type nested_dict: dict
  
      :param keys:
          Nested keys.
      :type keys: object
  
      :param default:
          Function used to initialize a new value.
      :type default: callable, optional
  
      :param init_nesting:
          Function used to initialize a new intermediate nesting dict.
      :type init_nesting: callable, optional
  
      :return:
          Value of nested-dictionary.
      :rtype: generator
      """
  
      if keys:
          default = default or init_nesting
          if keys[0] in nested_dict:
              nd = nested_dict[keys[0]]
          else:
              d = default() if len(keys) == 1 else init_nesting()
              nd = nested_dict[keys[0]] = d
          return get_nested_dicts(nd, *keys[1:], default=default,
                                  init_nesting=init_nesting)
      return nested_dict