def _adj_prices(ts):
    """
    Back adjust prices relative to adj_close for dividends and splits.

    Parameters
    ----------
    ts : pd.DataFrame
        The timeseries of a symbol.

    Returns
    -------
    pd.DataFrame
        The timeseries with adjusted prices.
    """
    ts['open'] = ts['open'] * ts['adj_close'] / ts['close']
    ts['high'] = ts['high'] * ts['adj_close'] / ts['close']
    ts['low'] = ts['low'] * ts['adj_close'] / ts['close']
    ts['close'] = ts['close'] * ts['adj_close'] / ts['close']
    return ts