def get_name_str(self, element):
        '''get_name_str

        High-level api: Produce a string that represents the name of a node.

        Parameters
        ----------

        element : `Element`
            A node in model tree.

        Returns
        -------

        str
            A string that represents the name of a node.
        '''

        if element.get('diff') == 'added':
            return self.model2.get_name_str(element)
        else:
            return self.model1.get_name_str(element)
get_name_str

        High-level api: Produce a string that represents the name of a node.

        Parameters
        ----------

        element : `Element`
            A node in model tree.

        Returns
        -------

        str
            A string that represents the name of a node.