def el_to_list(data, key1, key2, key3):
    """
    Extracts a value from the third layer of a dictionary given the
    three keys and converts it to a list if it is not a list
    """
    val = data[key1].get(key2, dict()).get(key3, [])
    if isinstance(val, list):
        return val
    else:
        return [val]