docs: def _set_prefix(self):
          """
          Called by ``__init()__`` to set the object's ``_prefix`` attribute,
          which determines the prefix app users must use when overriding
          settings associated with this helper. For example:
  
          If the ``_prefix`` attribute were to be set to "YOURAPP", and there
          exists an app setting called ``SETTING_NAME``, app users would override
          that setting by adding a variable with the name ``YOURAPP_SETTING_NAME``
          to their Django settings.
  
          Developers can choose their own prefix by setting the ``prefix``
          attribute on their helper class. If no value is specified, a deterministic
          default value is generated, based on the where the helper class is defined.
          For example:
  
          A helper class defined in ``yourapp/conf/settings.py`` or
          ``yourapp/settings.py`` would be assigned the prefix: ``"YOURAPP"``.
  
          A helper class is defined in ``yourapp/subapp/conf/settings.py`` or
          ``yourapp/subapp/settings.py`` would be assigned the prefix: ``"YOURAPP_SUBAPP"``.
          """
          if self.prefix is not None:
              value = self.prefix.rstrip('_')
          else:
              module_path_parts = self.__module_path_split[:-1]
              if module_path_parts[-1] == 'conf':
                  module_path_parts.pop()
              value = '_'.join(module_path_parts)
          self._prefix = value.upper()