pub fn next(&mut self, tree: &Tree) -> Option<NodeIndex> {
        if let Some(parent) = tree
            .graph()
            .neighbors_directed(self.cur, Direction::Incoming)
            .next()
        {
            self.cur = parent;
            Some(parent)
        } else {
            None
        }
    }
/// Moves up the tree by following the first incoming edge.
///
/// This method behaves like an iterator, returning `Some(NodeIndex)` before reaching the final
/// state. Calling this method again in the final state will return `None`.
Moves up the tree by following the first incoming edge.
This method behaves like an iterator, returning `Some(NodeIndex)` before reaching the final
state. Calling this method again in the final state will return `None`.
Moves up the tree by following the first incoming edge . This method behaves like an iterator returning ` Some ( NodeIndex ) ` before reaching the final state . Calling this method again in the final state will return ` None ` .
pub fn next(&mut self, tree: &Tree) -> Option<NodeIndex> {
        if let Some(parent) = tree
            .graph()
            .neighbors_directed(self.cur, Direction::Incoming)
            .next()
        {
            self.cur = parent;
            Some(parent)
        } else {
            None
        }
    }
pub fn next ( & mut self , tree : & Tree ) -> Option < NodeIndex > { if let Some ( parent ) = tree . graph ( ) . neighbors_directed ( self . cur , Direction :: Incoming ) . next ( ) { self . cur = parent ; Some ( parent ) } else { None } }
Moves up the tree by following the first incoming edge.
Moves up the tree by following the first incoming edge .
&mut self
tree
&Tree
&mut self
tree
&Tree