This annotation is to be used on a Groovy method which
is part of an Algebraic UDF to indicate that it will
act as the exec method of the 'Intermed' class of the UDF.
The value of the annotation is the name of the Algebraic UDF
it belongs to.
The annotated method MUST accept a single groovy.lang.Tuple parameter,
and MUST return a groovy.lang.Tuple or Object.