There is a bug in docs that I noticed recently. Here the top of the page an example is given regarding element animation control:
if(opt.anim.isAnimated()){ opt.anim.stop(); }
I tried to repeat this, but it appeared that opt.anim.isAnimated is just a boolean variable, not a function.

P.S. Sorry if the format of my post is incorrect, I assume that bugreport formatting guidelines don't apply to bugs in docs since it's browser- and platform-agnostic and there is no such stuff as test cases and debugging info.