slice(...args) {
    let slicedModels = this.models.slice(...args);

    return new Collection(this.modelName, slicedModels);
  }
Returns a new Collection with a subset of its models selected from `begin` to `end`.

    ```js
    let firstThreePosts = user.posts.slice(0, 3);
    ```

    @method slice
    @param {Integer} begin
    @param {Integer} end
    @return {Collection}
    @public