In matplotlib, what is the difference betweent set_xlim and set_xbound?

From the help:

set_xlim: Set the data limits for the xaxis.

set_xbound: Set the lower and upper numerical bounds of the x-axis.

That is not very clear, so let’s say that I plot something:

import matplotlib.pylab as plt
fig, ax = plt.subplots(1, 1)
ax.plot(xrange(10), xrange(10))

Now, either I do:

ax.set_xlim(2, 7)

or:

ax.set_xbound(2, 7)

I do not see the difference. I can dragg the plot, all the line is ploted between 0 and 9.