cmd.Cmd has a documented do_help(self, arg) method (written in 2000).  If arg is '', it prints
1. Documented commands (do_x with help_x or do_x.__doc__ != ''), sorted
2. Other help topics (help_y with no do_y), unsorted
3. Undocumented commands (do_ without no help_x and no do_x.__doc__), sorted

The dict called 'help' (which should be a set, and might better be called 'topics') ends up with a member for each help_y topic without a do_y command.  Not sorting the keys is at least a design bug.  Leaving users aside, it makes do_help unpredictable and hard to test.  Our test.test_cmd omits misc help topics.  In verbose mode, it prints

Trying:
    mycmd.do_help("")
Expecting:
    <BLANKLINE>
    Documented commands (type help <topic>):
    ========================================
    add  help
    <BLANKLINE>
    Undocumented commands:
    ======================
    exit  shell
    <BLANKLINE>
ok

As near as I can tell, text_cmd would still pass if Misc topics were removed and never printed.  Topics can only be added to the test above is they are dependably ordered (ie, sorted).

---
This '?' or 'help' case is also not properly documented, but should be.  3.4 cmd.__doc__ has this mishmash:

"With no arguments, it lists all topics with defined help_ functions, broken into up to three topics; documented commands, miscellaneous help topics, and undocumented commands."

3.4 doc says "With no argument, do_help() lists all available help topics (that is, all commands with corresponding help_*() methods or commands that have docstrings), and also lists any undocumented commands."