def _write_cache(df, path, cache_format):
    """
    Save the DataFrame to the cache-file on disk using the given format.

    :param df: Pandas DataFrame to be cached to disk.
    :param path: Full path for the cache-file.
    :param cache_format: String with the cache-format.
    :return: None
    """
    if cache_format.startswith('pickle'):
        df.to_pickle(path)
    elif cache_format == 'parquet':
        df.to_parquet(path)
    elif cache_format == 'feather':
        df.to_feather(path)
