Navigate from a node to its parent or return Option.none() if the tree is focused on a root node.
Option.none()
See up for an unsafe version.
The underlying type of the tree.
An updated zipper pointing at a new focus or Option.none() if zipper focus is on root node.
Navigate from a node to its parent or return
Option.none()if the tree is focused on a root node.See up for an unsafe version.