'Copies tree nodes from the old parser tree.
Returns the number of tree nodes that were copied.'

def copy_nodes(self, tree_nodes, until_line, line_offset):

    tos = self._get_insertion_node(tree_nodes[0])
    (new_nodes, self._tos) = self._copy_nodes(tos, tree_nodes, until_line, line_offset)
    return new_nodes
