try: #QGis 3.x
       QgsProject.instance().addMapLayer(vlayer, group is None)
except: #QGis 2.x
       QgsMapLayerRegistry.instance().addMapLayer(vlayer, group is None)

try: #QGis 3.x
      QgsProject.instance().removeMapLayer(layer.id())
except: #QGis 2.x
      QgsMapLayerRegistry.instance().removeMapLayers([layer.id()])