code: func (e *Explain) RenderResult() error {
  	if e.StmtPlan == nil {
  		return nil
  	}
  	switch strings.ToLower(e.Format) {
  	case ast.ExplainFormatROW:
  		e.explainedPlans = map[int]bool{}
  		e.explainPlanInRowFormat(e.StmtPlan.(PhysicalPlan), "root", "", true)
  	case ast.ExplainFormatDOT:
  		e.prepareDotInfo(e.StmtPlan.(PhysicalPlan))
  	default:
  		return errors.Errorf("explain format '%s' is not supported now", e.Format)
  	}
  	return nil
  }
docs: // RenderResult renders the explain result as specified format.