annotation: '//' predicate (iri | literal)

def visitAnnotation(self, ctx: ShExDocParser.AnnotationContext):
        """ annotation: '//' predicate (iri | literal) """
        # Annotations apply to the expression, NOT the shape (!)
        annot = Annotation(self.context.predicate_to_IRI(ctx.predicate()))
        if ctx.iri():
            annot.object = self.context.iri_to_iriref(ctx.iri())
        else:
            annot.object = self.context.literal_to_ObjectLiteral(ctx.literal())
        self.annotations.append(annot)