def ensure_primary_annotation_has_hook(annotation)
      hook = annotation.hook
      if hook.nil? then
        raise CaRuby::DatabaseError.new("Cannot save annotation #{annotation} since it does not reference a hook entity")
      end
      if hook.identifier.nil? then
        logger.debug { "Ensuring that the annotation #{annotation.qp} hook entity #{hook.qp} exists in the database..." }
        ensure_exists(hook)
      end
    end
def ensure_primary_annotation_has_hook(annotation)
      hook = annotation.hook
      if hook.nil? then
        raise CaRuby::DatabaseError.new("Cannot save annotation #{annotation} since it does not reference a hook entity")
      end
      if hook.identifier.nil? then
        logger.debug { "Ensuring that the annotation #{annotation.qp} hook entity #{hook.qp} exists in the database..." }
        ensure_exists(hook)
      end
    end
Ensures that a primary annotation hook exists.

 @param (see #prepare_annotation_for_save)
 @raise [CaRuby::DatabaseError] if the annotation does not reference a hook entity