code: func (g *Graph) ThisString(def ...string) string {
  
  	// If g is nil, return default or nothing
  	if g == nil {
  		if len(def) == 0 {
  			return ""
  		}
  		return def[0]
  	}
  
  	return _string(g.This)
  }
docs: // ThisString returns the current node content as a string