The class represents the final stage in a push-mode tuple pipeline. The previous stages
have stored the values corresponding to the current tuple in local variables on the
stack; all that remains is to evaluate the return expression (with reference to these
variables) and send the results to the current receiver.
Notify the availability of the next tuple. Before calling this method,
the supplier of the tuples must set all the variables corresponding
to the supplied tuple in the local stack frame associated with the context object