Loading a GeoJSON in QGIS using Python but the layer can't be edited

def loadLayer(self):
    layer = self.dlg.listWidget.currentItem().text()
    url = self.getRoute(layer)
    data_req = requests.get(url)
    data_layer = data_req.json()
    with open('xx.geojson','w+') as f:
        json.dump(data_layer,f)
    layer = QgsVectorLayer('xx.geojson',layer,' ogr')
    QgsProject.instance().addMapLayers([layer])

I’m getting data from a server in the form of a feature collection. I write it into a GeoJSON file then load it in QGIS. The layer loads properly but if I try to edit some features it is not possible.