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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def update(gandi, address, dest_add, dest_del):
 """Update a domain mail forward."""

    source, domain = address

    if not dest_add and not dest_del:
        gandi.echo('Nothing to update: you must provide destinations to '
                   'update, use --dest-add/-a or -dest-del/-d parameters.')
        return

    result = gandi.forward.update(domain, source, dest_add, dest_del)

    return result