<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _filter_repeating_items(download_list):
 """ Because of data_filter some requests in download list might be the same. In order not to download them again this method will reduce the list of requests. It will also return a mapping list which can be used to reconstruct the previous list of download requests. :param download_list: List of download requests :type download_list: list(sentinelhub.DownloadRequest) :return: reduced download list with unique requests and mapping list :rtype: (list(sentinelhub.DownloadRequest), list(int)) """

        unique_requests_map = {}
        mapping_list = []
        unique_download_list = []
        for download_request in download_list:
            if download_request not in unique_requests_map:
                unique_requests_map[download_request] = len(unique_download_list)
                unique_download_list.append(download_request)
            mapping_list.append(unique_requests_map[download_request])
        return unique_download_list, mapping_list