code: func (expr *ScalarFunction) ExplainInfo() string {
  	var buffer bytes.Buffer
  	fmt.Fprintf(&buffer, "%s(", expr.FuncName.L)
  	for i, arg := range expr.GetArgs() {
  		buffer.WriteString(arg.ExplainInfo())
  		if i+1 < len(expr.GetArgs()) {
  			buffer.WriteString(", ")
  		}
  	}
  	buffer.WriteString(")")
  	return buffer.String()
  }
docs: // ExplainInfo implements the Expression interface.