code: function(arr, world, refText, refTerms) {
    this.terms = arr;
    this.world = world || w;
    this.refText = refText;
    this._refTerms = refTerms;
    this.get = n => {
      return this.terms[n];
    };
    //apply getters
    let keys = Object.keys(getters);
    for (let i = 0; i < keys.length; i++) {
      Object.defineProperty(this, keys[i], getters[keys[i]]);
    }
  }
docs: Terms is an array of Term objects, and methods that wrap around them