CreateWrappedGP         Factory function called by GPNode to create the
                        wrapper for a specified GP package
GPNode                  R6 Class for the nodes / leaves in the GPTree
                        tree
GPTree                  Tree structure storing all nodes containing
                        local GPs
WrappedDiceKrigingGP    R6 class WrappedDiceKrigingGP
WrappedGP               R6 class WrappedGP
WrappedmlegpGP          R6 class WrappedmlegpGP
