</li>
	<li>An element list that does not contain any keys must
	    list an element for each struct field in the
	    order in which the fields are declared.
	</li>
	<li>If any element has a key, every element must have a key.
	</li>
	<li>An element list that contains keys does not need to
	    have an element for each struct field. Omitted fields