VSE: allow retiming keys to be manipulated via Python

There are various retiming_* operators . I can run some of them in a useful way, like adding retiming keys.

If I have a retiming key selected I can run more of them in a useful way, like changing their speed or adding a speed transition.

But I can't find a way to actually select a particular key, even one just added with retiming_key_add .

I can see some of their information eg strip.retiming_keys[1].timeline_frame , but I see no way to select them.

If I'm missing something please tell me! (I don't think so though; I asked some time ago over at Stack Exchange but had no responses.)

But otherwise this is something I'd love to see added. With the ability to select particular retiming keys I'd then be able to script retiming operations, such as having a macro to "fast-forward" a section of a video clip with nice speed ramps on either end.