Given a leaf_type and a root_type which is contained in its
anchestry, return the type that root_type is the immediate parent
of. In other words, this function determines the type that is
derived directly from root_type which is also a base class of
leaf_type. Given a root type and a leaf type, this function can
be used to determine the types and order in which the leaf type is
descended from the root type.
Given a leaf_type and a root_type which is contained in its anchestry, return the type that root_type is the immediate parent of. In other words, this function determines the type that is derived directly from root_type which is also a base class of leaf_type. Given a root type and a leaf type, this function can be used to determine the types and order in which the leaf type is descended from the root type.