[Orgmode] sorting a single todo kw by inactive timestamp

[Samuel Wales]

I have siblings with various todo kw.  I would like to sort just the
ones with a certain todo kw (which, if it makes it easier, can be
considered to be contiguous) by the first inactive timestamp.  I want
all the other nodes to not be changed in any way.

Does anybody have safe code for doing this type of thing?  Perhaps the
way it is done is to select a region of a bunch of contiguous nodes
that have a given todo kw, but I don't want to reinvent regexps or
figure out all the ways that such code could be brittle.  This is to
be called automatically.

Thanks.