def is_valid_arrangement(arrangement, song):
    """
    Validates an arrangement against a song. Returns True (valid) or
    False (invalid). Valid means that every setion specified in the
    arrangement exists in the song's specified sections.

    :param song: a dictionary conforming to the Song object data model.
    :param arrangement: a list specifying the arrangement of the song.

    :returns: `is_valid`, indicating whether the arrangement is valid.
    :rtype: `bool`
    """

    is_valid = True
    for section in arrangement:
        if section not in song["lyrics"].keys():
            is_valid = False
            print(f'{section} not in {song["lyrics"].keys()}')
            break
    return is_valid