code: def create_annotation(hook, annotation)
        # validate the arguments
        if hook.nil? then raise ArgumentError.new("Annotated caTissue object is missing") end
        if annotation.nil? then raise ArgumentError.new("Annotation caTissue object is missing") end
        # the annotated object must exist in the database
        unless hook.identifier then
          raise AnnotationError.new("Annotation writer does not support annotation of a caTissue object without an identifier: #{hook}")
        end
        # load the caRuby annotations if necessary
        hook.class.ensure_annotations_loaded
        # set the annotation hook reference
        annotation.hook = hook
        # create the annotation in the database
        annotation.create
      end
docs: Creates a new annotation object in the caTissue database.
  
   @param [CaTissue::Resource] hook the existing static hook object to annotate
   @param [CaTissue::Annotation] annotation the annotation object to create
   @raise [AnnotationError] if the hook object does not have a database identifier