Clarify descriptions of some operations; it's not always clear that strings are not actually modified.  Problem reported by Dr. Peter Stoehr <peter.stoehr@weihenstephan.org>.
Clarify descriptions of some operations; it's not always clear that
strings are not actually modified.  Problem reported by Dr. Peter
Stoehr <peter.stoehr@weihenstephan.org>.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator