docs: def item_meta(item_name, name, value, scheme=None):
      """
      Adds meta information to an already defined item
      of the model being defined.
      @param item_name: name of the model item the meta data should be added to.
      @type item_name: str or unicode
      @param name: name of the meta data class
      @type name: str or unicode
      @param value: metadata value
      @type value: str or unicode
      @param scheme: format information about the value
      @type scheme: str or unicode or None
      """
      _annotate("item_meta", item_name, name, value, scheme=scheme)