def _outer_to_numpy_indexer(key, shape):
    """Convert an OuterIndexer into an indexer for NumPy.

    Parameters
    ----------
    key : Basic/OuterIndexer
        An indexer to convert.
    shape : tuple
        Shape of the array subject to the indexing.

    Returns
    -------
    tuple
        Tuple suitable for use to index a NumPy array.
    """
    if len([k for k in key.tuple if not isinstance(k, slice)]) <= 1:
        # If there is only one vector and all others are slice,
        # it can be safely used in mixed basic/advanced indexing.
        # Boolean index should already be converted to integer array.
        return key.tuple
    else:
        return _outer_to_vectorized_indexer(key, shape).tuple