'Add a public ``add_x()`` method to the parent element class.'

def _add_public_adder(self):

    def add_child(obj):
        private_add_method = getattr(obj, self._add_method_name)
        child = private_add_method()
        return child
    add_child.__doc__ = ('Add    a    new    ``<%s>``    child    element    unconditionally,    inserted    in    the    correct    sequence.' % self._nsptagname)
    self._add_to_class(self._public_add_method_name, add_child)
