prolog:help_hook(+Action)Hook into help/0 
and help/1. 
If the hook succeeds, the built-in actions are not executed. For 
example, ?- help(picture). is caught by the XPCE help hook 
to give help on the class picture. Defined actions are:
- help
- User entered plain help/0 
to give default help. The default performs
help(help/1), 
giving help on help.
- help(What)
- Hook in help/1 
on the topic What.
- apropos(What)
- Hook in apropos/1 
on the topic What.