API for address book? (filter 'if in address book')

[Bryce Nesbitt]

Excuse the novice question: but where can I find the documentation on 
the API for accessing the address book module?

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Specifically I'd like to provide an email address and ask the address 
book module 'is it there'?  I would then modify Mozilla to support 
filters like:

    If sender is [in the address book] then
    send to [SPAM-Free Mailbox]

                -Bryce