def _auto_correlations(n_states):
    """Returns list of autocorrelations

    Args:
        n_states: number of local states

    Returns:
        list of tuples for autocorrelations

    >>> l = _auto_correlations(np.arange(3))
    >>> assert l == [(0, 0), (1, 1), (2, 2)]
    """
    local_states = n_states
    return [(l, l) for l in local_states]