code: func (p *Panel) GetTargets() *[]Target {
  	switch p.OfType {
  	case GraphType:
  		return &p.GraphPanel.Targets
  	case SinglestatType:
  		return &p.SinglestatPanel.Targets
  	case TableType:
  		return &p.TablePanel.Targets
  	default:
  		return nil
  	}
  }
docs: // GetTargets is iterate over all panel targets. It just returns nil if
  // no targets defined for panel of concrete type.