<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def list_items(self, url, container=None, last_obj=None, spr=False):
 """Builds a long list of objects found in a container. NOTE: This could be millions of Objects. :param url: :param container: :param last_obj: :param spr: "single page return" Limit the returned data to one page :type spr: ``bol`` :return None | list: """


        headers, container_uri = self._return_base_data(
            url=url,
            container=container
        )

        if container:
            resp = self._header_getter(uri=container_uri, headers=headers)
            if resp.status_code == 404:
                LOG.info('Container [ %s ] not found.', container)
                return [resp]

        return self._list_getter(
            uri=container_uri,
            headers=headers,
            last_obj=last_obj,
            spr=spr
        )