New in version 2.0.
Copy written duration and multiplier from source_leaf to target_leaf:
abjad> note = Note("c'4")
abjad> note.duration_multiplier = Duration(1, 2)
abjad> rest = Rest((1, 64))
abjad> leaftools.copy_written_duration_and_multiplier_from_leaf_to_leaf(note, rest)
Rest('r4 * 1/2')
Return target_leaf.