如何向joi.any()添加验证函数？

const Joi = require('joi');

const customJoi = Joi.extend((joi) => ({
  base: joi.any(),
  name: 'any',
  language: {
    customValidation: 'must be a valid value'
  },
  rules: [
    {
      name: 'customValidation',
      validate(params, value, state, options) {
        // 在这里编写自定义验证函数的逻辑
        // 如果验证通过，返回value；否则，返回this.createError()方法创建的错误信息
      }
    }
  ]
}));

const schema = customJoi.any().customValidation();
const result = schema.validate('example');

if (result.error) {
  console.log(result.error.details[0].message); // 输出错误信息
} else {
  console.log('Validation passed'); // 验证通过
}