if not io.check_files_existence(self.data_folder, filenames):
            # Download and unpack.
            url = "https://zenodo.org/record/841984/files/wili-2018.zip?download=1"
            zipfile_name = "wili-2018.zip"
            io.download_extract_zip_file(self.logger, self.data_folder, url, zipfile_name)