Get a list of all leafs in a tree by recursively searching the tree starting
at the given node (if not data object is given. If data is
given, the function returns the leafs that are predicted for each row of the
given data.
getLeafs(tree, data = NULL)A semtree object
A data.frame
Brandmaier, A.M., Oertzen, T. v., McArdle, J.J., & Lindenberger, U. (2013). Structural equation model trees. Psychological Methods, 18(1), 71-86.