The default request keyword arguments to be passed to the requests library.

def _default_request_kwargs(self):
        """The default request keyword arguments to be passed to the requests library."""
        defaults = copy.deepcopy(super(Acls, self)._default_request_kwargs)
        defaults.setdefault('headers', {}).update({
            'X-Auth-Token': self._client.auth._token
        })
        return defaults