public function offsetGet($offset) : ?Collection {
        return $this->has($offset) ? $this->collection($offset) : null;
    }
public function offsetGet($offset) : ?Collection {
        return $this->has($offset) ? $this->collection($offset) : null;
    }
public function offsetGet ( $ offset ) : ? Collection { return $ this -> has ( $ offset ) ? $ this -> collection ( $ offset ) : null ; }
Get a collection offset.

@param  string  $offset
Get a collection offset .