@staticmethod<EOL><INDENT>def copy_node(ret, element, msg):<DEDENT>
sub_element = etree.SubElement(ret, element.tag, attrib=element.attrib)<EOL>ModelDiff.process_attrib(sub_element, msg)<EOL>return sub_element<EOL>
copy_node

        High-level api: Copy element as a node without its children and put it
        as a child of ret.

        Parameters
        ----------

        element : `Element`
            A node in a model tree.

        msg : `str`
            Message to be added.

        ret : `Element`
            A node in self.tree.

        Returns
        -------

        None
            Nothing returns.