tick formatter pi cause the plot of squared sine function to have long tick label

edit

sage: plot(sin(x)^2)

This is normal. but if you use the below code:

sage: plot(sin(x)^2, tick_formatter=pi)

You will get very long y axis tick labels.

The version of sagemath is 9.6-2, from arch linux package repository.

edit: tick_formatter=[pi, None] will give the normal result, but according to the documentation of Graphics objects, about tick_formatter:

If the value of this keyword is a single item, then this will give the formatting for the horizontal axis only (except for the "latex" option).

So my code should work, but it did not work.