You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: hint_processor.go
    path of file: ./repos/tidb/pkg/util/hint
    
    the code of the file until where you have to start completion: // Copyright 2020 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or ag
    
func (checker *bindableChecker) Enter(in ast.Node) (out ast.Node, skipChildren bool) {
	switch node := in.(type) {
	case *ast.ExistsSubqueryExpr, *ast.SubqueryExpr:
		checker.bindable = false
		checker.reason = errors.New("can't create binding for query with sub query")
		return in, true
	case *ast.TableName:
		if _, ok := checker.tables[node.Schema]; !ok {
			checker.tables[node.Name] = struct{}{}
		}
		if len(checker.tables) >= 3 {
			checker.bindable = false
			checker.reason = errors.New("can't create binding for query with more than two table join")
			return in, true
		}
	}
	return in, false
}