findBy(query) {
    let record = this._findRecordBy(query);
    if (!record) {
      return null;
    }

    // Return a copy
    return duplicate(record);
  }
Returns the first model from `collection` that matches the
    key-value pairs in the `query` object. Note that a string
    comparison is used. `query` is a POJO.

    ```js
    // Given users = [ { id: 1, name: 'Link' }, { id: 2, name: 'Zelda' } ]
    db.users.findBy({ name: 'Link' }); // { id: 1, name: 'Link' }
    ```

    @method find
    @param query
    @public