|| This is the base class for all visitors.
For each AST node, this class will provide
a bare-bones method for traversal.
|| This class is simply a visitor implementation
that traverses the AST, produced by the Velocity
parsing process, and creates a visual structure
of the AST. This is primarily used for
debugging, but it useful for documentation
This class is a visitor used by the VM proxy to change the
literal representation of a reference in a VM. The reason is
to preserve the 'render literal if null' behavior w/o making
the VMProxy stuff more complicated than it is already.