def ancestors_root(self):
if self.is_root():<EOL><INDENT>return []<EOL><DEDENT>ancestors = set([])<EOL>self._depth_ascend(self, ancestors, True)<EOL>try:<EOL><INDENT>ancestors.remove(self)<EOL><DEDENT>except KeyError:<EOL><INDENT>pass<EOL><DEDENT>return list(ancestors)<EOL>
Returns a list of the ancestors of this node but does not pass the
        root node, even if the root has parents due to cycles.