final public function collection($name = '')
    {
        return new self($this->collection, $this->name.$name, $this, $this->prefixes);
    }
final public function collection($name = '')
    {
        return new self($this->collection, $this->name.$name, $this, $this->prefixes);
    }
final public function collection ( $ name = '' ) { return new self ( $ this -> collection , $ this -> name . $ name , $ this , $ this -> prefixes ) ; }
Creates a sub-collection.

@return self
Creates a sub - collection .