如何从 function 返回 pyplot 轴，以便可以将其设置为不同 function 中的轴？

Question

I have a function which plots a basic histogram. I want this function to return the figure/axis of this histogram such that I can, in a different function, call this histogram function and set the return value as an axis in the new function. Example to make this more clear:

def histogrammer():
    fig, ax = plt.subplots()
    ax.hist(data)
    return ax

def function2():
    fig, axs = plt.subplots(2)
    axs[0].plot(x, y)
    axs[1] = histogrammer()
    axs[1].axvline(X_0)

Doing this doesn't actually set axs[1] as the axis from the histogrammer function, as it doesn't add a vertical line at X_0. It does however cause histogrammer() to be printed to the screen. If it matters, this is Python 2.7