docs: function (Vue) {
    var ref = Vue.util;
    var extend = ref.extend;
  
    // set global validators asset
    var assets = Object.create(null);
    extend(assets, validators);
    Vue.options.validators = assets;
  
    // set option merge strategy
    var strats = Vue.config.optionMergeStrategies;
    if (strats) {
      strats.validators = function (parent, child) {
        if (!child) { return parent }
        if (!parent) { return child }
        var ret = Object.create(null);
        extend(ret, parent);
        var key;
        for (key in child) {
          ret[key] = child[key];
        }
        return ret
      };
    }
  
    /**
     * Register or retrieve a global validator definition.
     */
    function validator (
      id,
      def
    ) {
      if (def === undefined) {
        return Vue.options['validators'][id]
      } else {
        Vue.options['validators'][id] = def;
        if (def === null) {
          delete Vue.options['validators']['id'];
        }
      }
    }
    Vue['validator'] = validator;
  }