def _clean_ylabel(feature, max_length=20):
    """
    Replaces underscores with spaces and splits `feature` based on line length

    Parameters
    ----------
    feature : str
        String to be cleaned
    max_length : str
        Maximum length (in characters) of each line. If `feature` is longer
        than this length it will be split with a newline character. Default: 20

    Returns
    -------
    feature : str
        Cleaned input `feature`
    """

    feature = feature.replace('_', ' ')
    if len(feature) > max_length:
        ylabel = feature.split(' ')
        idx = len(ylabel) // 2
        feature = '\n'.join([' '.join(ylabel[:idx]), ' '.join(ylabel[idx:])])
    return feature