In my standalone script I want to use the SAGA tool "merge vector layers". According to the docs I need the [following][1].

Thus, I wrote the following code to implement the tool: 

    def merge(self):
        Parcel_channel2 = self.Parcel_Channel2()
        intersection = self.intersection()
        param = {'INPUT': [Parcel_channel2, intersection],
                 'MERGED': 'TEMPORARY_OUTPUT',
                 'SRCINFO': False,
                 'MATCH': True,
                 }
        merge = processing.run('saga:mergevectorlayers', param)
        vlayer = merge['MERGED']
        QgsProject.instance().addMapLayer(vlayer)
        return vlayer

When I try to run the script I get the following error message: 

> QgsProject.addMapLayer(): argument 1 has unexpected type 'str' 

With native Qgs tools, this code works fine. However, it seems that SAGA doesn't return a VectorLayer but just the string in my 'outDir' variable. How do I get the output when using SAGA?

I'm using QGIS 3.10

Edit: I figured out, that native Qgs tools retun QgsMapLayer objects and saga tools return the path and name of a .shp file

> C:/Users/denni/AppData/Local/Temp/processing_c0c1104bbc4447558e00113072ccc4d8/91e580e9c006429597540594cb000407/MERGED.shp

but I need a QgsMapLayer as result... how would I do that?

  [1]: http://www.saga-gis.org/saga_tool_doc/2.3.0/shapes_tools_2.html
  [2]: https://i.sstatic.net/UvIFB.png