Pruning refers to removing entire subtrees. This function has side-effects, it modifies your data.tree structure!
Usage
Prune(node, pruneFun)
Value
the number of nodes removed
Arguments
node
The root of the sub-tree to be pruned
pruneFun
allows providing a prune criteria, i.e. a function taking a Node as an input, and returning TRUE or FALSE.
If the pruneFun returns FALSE for a Node, then the Node and its entire sub-tree will not be considered.