(node_map)
return 0 in node_map
check if current to split is root node
check if current to split is root node
check if current to split is root node
def _is_root_node(node_map):

        """
        check if current to split is root node
        """
        return 0 in node_map
def _is_root_node ( node_map ) : return 0 in node_map