code: func (t *TextView) Highlight(regionIDs ...string) *TextView {
  	t.highlights = make(map[string]struct{})
  	for _, id := range regionIDs {
  		if id == "" {
  			continue
  		}
  		t.highlights[id] = struct{}{}
  	}
  	t.index = nil
  	return t
  }
docs: // Highlight specifies which regions should be highlighted. See class
  // description for details on regions. Empty region strings are ignored.
  //
  // Text in highlighted regions will be drawn inverted, i.e. with their
  // background and foreground colors swapped.
  //
  // Calling this function will remove any previous highlights. To remove all
  // highlights, call this function without any arguments.