code: function(items, config) {
  
    config = config || {};
    config.searchableFields = config.searchableFields || [];
    this.items = items;
    // creating index
    this.idx = lunr(function () {
      // currently schema hardcoded
      this.field('name', { boost: 10 });
  
      var self = this;
      _.forEach(config.searchableFields, function(field) {
        self.field(field);
      });
      this.ref('id');
    })
    //var items2 = _.clone(items)
    var i = 1;
    _.map(items, (doc) => {
  
      if (!doc.id) {
        doc.id = i;
        ++i;
      }
      this.idx.add(doc)
    })
  
    this.store = _.mapKeys(items, (doc) => {
      return doc.id;
    })
  }
docs: responsible for making full text searching on items
  config provide only searchableFields