Improve documentation

Author: hansthen

Doc/library/argparse.rst

@@ -1135,16 +1135,16 @@ from *dest*.  This is usually what you want because the user never sees the
 *dest* parameter.  If this display isn't desirable (perhaps because there are
 many choices), just specify an explicit metavar_.
 
+
 .. _convert_choices:
 
 convert_choices
 ^^^^^^^^^^^^^^^
 
 By default, when a user passes both a ``type`` and a ``choices`` argument, the
 ``choices`` need to be specified in the target type, after conversion.
-This can cause confusing ``usage`` and ``help`` strings. If the user would like
-to specify ``choices`` in the same vocabulary as the end-user would enter them,
-this feature can be enabled by setting ``convert_choices`` to ``True``::
+This can cause confusing ``usage`` and ``help`` strings.
+To specify ``choices`` before conversion, set the flag ``convert_choices``.
 
    >>> parser = argparse.ArgumentParser()
    >>> parser.add_argument('when',