QgsVectorFileWriter::writeAsVectorFormat  (QgsVectorLayer * layer,
                                           const QString &  fileName,
                                           const QString &  fileEncoding,
                                           const QgsCoordinateReferenceSystem &
                                                  destCRS = QgsCoordinateReferenceSystem(),
                                           const QString &  driverName = "GPKG",
                                           .
                                           .
                                           .