code: func (pc *paramMarkerInPrepareChecker) Enter(in ast.Node) (out ast.Node, skipChildren bool) {
  	switch v := in.(type) {
  	case *driver.ParamMarkerExpr:
  		pc.inPrepareStmt = !v.InExecute
  		return v, true
  	}
  	return in, false
  }
docs: // Enter implements Visitor Interface.