'Add parents to this role. Also should override if neccessary.
Example::
editor_of_articles = RoleMixin(\'editor_of_articles\')
editor_of_photonews = RoleMixin(\'editor_of_photonews\')
editor_of_all = RoleMixin(\'editor_of_all\')
editor_of_all.add_parents(editor_of_articles, editor_of_photonews)
:param parents: Parents to add.'

def add_parents(self, *parents):

    for parent in parents:
        self.add_parent(parent)
