Implements (well enough for our purposes) DOM node import.

def importNode(self, document, node, deep=0):
        """Implements (well enough for our purposes) DOM node import."""
        nodetype = node.nodeType
        if nodetype in (node.DOCUMENT_NODE, node.DOCUMENT_TYPE_NODE):
            raise DOMException('Illegal node type for importNode')
        if nodetype == node.ENTITY_REFERENCE_NODE:
            deep = 0
        clone = node.cloneNode(deep)
        self._setOwnerDoc(document, clone)
        clone.__imported__ = 1
        return clone