def METHOD_NAME(self):
    r"""
    Returns the zero of this additive monoid, as per :meth:`CommutativeAdditiveMonoids.ParentMethods.zero`.
    EXAMPLES::
        sage: M = CommutativeAdditiveMonoids().example(); M
        An example of a commutative monoid: the free commutative monoid generated by ('a', 'b', 'c', 'd')
        sage: M.zero()
        0
    """
    return self(())