SWI-Prolog -- prolog:help

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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.