def _genpoints(xlist, lbound, ubound):
    """Generate the points necessary to plot the lines showing the interval estimates.

    Parameters
    ----------
    xlist : array_like
        Array of values on the x-axis.
    lbound : array_like
        Lower bounds of the estimates.
    ubound : array_like
        Upper bounds of the estimates.

    Returns
    -------
    points : list
        List of start and end points for plotting the interval estimates.
    """
    xlist = xlist.tolist().copy()
    lbound = lbound.tolist().copy()
    ubound = ubound.tolist().copy()
    # Alternative approach -> shorter, seen in
    # https://pandas.pydata.org/docs/getting_started/10min.html Stack example
    xtemp = list(zip(*[xlist, xlist]))
    inttemp = list(zip(*[lbound, ubound]))
    points = []
    for xnew, ynew in zip(xtemp, inttemp):
        points.append(list(zip(xnew, ynew)))

    return points