code: private Document getProjectionDocument() {
  		if ( projections.isEmpty() ) {
  			return null;
  		}
  
  		Document projectionDocument = new Document();
  
  		for ( String projection : projections ) {
  			projectionDocument.put( projection, 1 );
  		}
  
  		return projectionDocument;
  	}
docs: Returns the projection columns of the parsed query in form of a {@code Document} as expected by MongoDB.
  
  @return a {@code Document} representing the projections of the query