animated frames do not match the same frames when plotted

[llsoft2000]

Hi,

first of all, I would like to express my appreciation for this great python package.

I did some experiments with SE3 objects and animations and found a behavior of the animate method that I can't explain.
If SE3 is animated without the start argument, everything works as expected. The same applies if you explicitly start at SE3(). However, if the start is an arbitrary pose, the animated frame does not start in the expected pose and does not end at the pose for which animate is called.

t = SE3([
    SE3(),
    SE3([-1,0,2]),  # start
    SE3.RPY([10, 5, -20], unit='deg') * SE3([1,2,1]), # end
])
t[0].plot(frame='0', color='black')
t[1].plot(frame='1', color='blue')
t[2].plot(frame='2', color='red')
t[2].animate(frame='2m', start=t[1], color='purple')    # frame does not move from t[1] to t[2] as I would expect
# t[2].animate(frame='2m', start=t[0], color='purple')  # ok, frame moves from t[0] to [2]
# t[2].animate(frame='2m', color='purple')              # ok, frame moves from origin to t[2]

I have also summarized the experiment in a jupyter notebook animate_start_to_end.ipynb.json (remove the json ending to open it as notebook).
Can you please check it and let me know if I am doing something wrong.

Best regards.