here and visitor
At every execution point in a Jac/Jaseci program there are two scopes visible, that of the
walker, and that of the node it is executing on. These contexts can be referenced with the
special variables here and visitor respectively. Walkers use here to refer to the context of
the node it is currently executing on, and abilities can use visitor to refer to the context of
the current walker executing. Think of these are special this references.