docs: function(beginIndex, endIndex) {
          var ret = Ember.A();
          var length = get(this, 'length');
  
          if (isNone(beginIndex)) {
            beginIndex = 0;
          }
  
          if (isNone(endIndex) || (endIndex > length)) {
            endIndex = length;
          }
  
          if (beginIndex < 0) {
            beginIndex = length + beginIndex;
          }
  
          if (endIndex < 0) {
            endIndex = length + endIndex;
          }
  
          while (beginIndex < endIndex) {
            ret[ret.length] = this.objectAt(beginIndex++);
          }
  
          return ret;
        }