def get_file_diff(self, files_to_diff):
        """ get_file_diff: retrieves list of files that do not exist on content curation server
            Args: None
            Returns: list of files that are not on server
        """
        file_diff_result = []
        chunks = [files_to_diff[x:x+1000] for x in range(0, len(files_to_diff), 1000)]
        file_count = 0
        total_count = len(files_to_diff)
        for chunk in chunks:
            response = config.SESSION.post(config.file_diff_url(), data=json.dumps(chunk))
            response.raise_for_status()
            file_diff_result += json.loads(response._content.decode("utf-8"))
            file_count += len(chunk)
            config.LOGGER.info("\tGot file diff for {0} out of {1} files".format(file_count, total_count))

        return file_diff_result
get_file_diff: retrieves list of files that do not exist on content curation server
            Args: None
            Returns: list of files that are not on server