Create an element as a child of this SLDNode.

        @type    ns: string
        @param   ns: The namespace of the new element.
        @type  name: string
        @param name: The name of the new element.
        @rtype: L{SLDNode}
        @return: The wrapped node, in the parent's property class. This will
                 always be a descendent of SLDNode.

def create_element(self, ns, name):
        """
        Create an element as a child of this SLDNode.

        @type    ns: string
        @param   ns: The namespace of the new element.
        @type  name: string
        @param name: The name of the new element.
        @rtype: L{SLDNode}
        @return: The wrapped node, in the parent's property class. This will
                 always be a descendent of SLDNode.
        """
        elem = self._node.makeelement('{%s}%s' % (SLDNode._nsmap[ns], name), nsmap=SLDNode._nsmap)
        self._node.append(elem)

        return getattr(self, name)