size and pickling time.

namespace as string.

when applicable.

on OS-X. Patch by Jeff Ramnani.

This has come up often enough now on the tracker that it deserves a FAQ entry.

* Describe compress() and accumulate()
* Add a subsection on combinatoric functions.
* Add a forward link to skip the theoretical discussion in the first section.
* Clarify what filterfalse() is the opposite of.
* Remove the old outline and some notes at the end.
* Various small edits.

initial patch by Trent Nelson.

is imported. Instead, ElementTree.parse can look for a special internal method
defined by the accelerator.

This is useful when mucking with import_fresh_module to either force or block
importing of the _elementtree accelerator. These tests in place provide an
immediate indication whether the accelerator was actually imported and overrode
the classes it should have.

Renaming to _Element_Py for clarity and moving it to a more logical location.
_ElementInterface OTOH is unused and is therefore removed.

Close #17988

Also clean up some code around this