I'm getting runtime error Invalid mxd filename
>>> import arcpy
...
... mxd_empty = "c:\project\Output"
...
... mxd = arcpy.mapping.MapDocument("CURRENT")
... for lyr in arcpy.mapping.ListLayers(mxd):
... mxde = arcpy.mapping.MapDocument(mxd_empty)
... dfe = arcpy.mapping.ListDataFrames(mxde)[0]
... arcpy.mapping.AddLayer(dfe, lyr)
... mxde.saveACopy(r"C:\Project\Output\\" + lyr.name + ".mxd")
...
... del lyr, mxd, dfe, mxde
...
Runtime error
Traceback (most recent call last):
File "<string>", line 7, in <module>
File "c:\program files (x86)\arcgis\desktop10.6\arcpy\arcpy\arcobjects\mixins.py", line 651, in __init__
assert (os.path.isfile(mxd) or (mxd.lower() == "current")), gp.getIDMessage(89004, "Invalid MXD filename")
AssertionError: Invalid MXD filename.