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1 The Py_INCREF(_code) at line 86 is the same as in
  your original code; it should guarantee that the
  code object doesn't go away.  However, I forgot
  the corresponding Py_DECREF()...

2 It was a quick hack to have help(lsprof) display
  these types as well.  Now I'm no longer sure that
  we need help(lsprof) to display them anyway, so
  let's use the standard '_lsprof.XXX' names.

3 Profiling a large program took forever.  I
  interrupted it after 30 minutes when it showed no
  sign of wanting to go past the initial step that
  normally takes only a few minutes.  With rotating
  trees this step is fast again.  Maybe they are not
  an optimal structure, though, because it still
  takes something like three times longer to finish
  the whole program (normally takes half an hour).

4 No.

Checked in your proposed changes.  What is still
missing: deciding how much similar to the
profiler.py and pstats.py API we need to be, and
writing some tests (ideally, having good test
coverage would be nice).