How to use the shyaml.IndexNotIntegerError function in shyaml

>>> aget({'x': 1}, ())
        {'x': 1}

    """
    key = iter(key)
    try:
        head = next(key)
    except StopIteration:
        return dct

    if isinstance(dct, list):
        try:
            idx = int(head)
        except ValueError:
            raise IndexNotIntegerError(
                "non-integer index %r provided on a list."
                % head)
        try:
            value = dct[idx]
        except IndexError:
            raise IndexOutOfRange(
                "index %d is out of range (%d elements in list)."
                % (idx, len(dct)))
    else:
        try:
            value = dct[head]
        except KeyError:
            ## Replace with a more informative KeyError
            raise MissingKeyError(
                "missing key %r in dict."
                % (head, ))