public function project() : Stage\Project
    {
        $stage = new Stage\Project($this);
        $this->addStage($stage);

        return $stage;
    }
public function project() : Stage\Project
    {
        $stage = new Stage\Project($this);
        $this->addStage($stage);

        return $stage;
    }
public function project ( ) : Stage \ Project { $ stage = new Stage \ Project ( $ this ) ; $ this -> addStage ( $ stage ) ; return $ stage ; }
Passes along the documents with only the specified fields to the next
stage in the pipeline. The specified fields can be existing fields from
the input documents or newly computed fields.

@see http://docs.mongodb.org/manual/reference/operator/aggregation/project/
Passes along the documents with only the specified fields to the next stage in the pipeline . The specified fields can be existing fields from the input documents or newly computed fields .