Rails - Jan 2012 - there is no documentation about before_add_for methods?

I''ve found nothing about the method in subject.
If, for a has_many :though => managements association I do:

Model.new.methods.grep(/management/)

I see some methods like:

:after_remove_for_managements, :before_add_for_managements=,
:before_add_for_managements

and others similar.
What those methods do?

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