def feature_name(n):  # pragma: no cover
    """normalize a feature name as encountered as column header in features.tsv

    converts camel case into space separated lowercase words.
    """
    chars = []
    for char in n:
        if char.isupper():
            chars.append(' ' + char.lower())
        else:
            chars.append(char)
    return ''.join(chars)