An annotation which attaches to a CoreLabel to denote that this is an operator in natural logic,
to describe which operator it is, and to give the scope of its argument(s).
This only attaches to tokens which are operators (i.e., the head words of operators).
Returns the type associated with this annotation. This method must
return the same class type as its value type parameter. It feels like
one should be able to get away without this method, but because Java
erases the generic type signature, that info disappears at runtime.