Add a topology and its associated layers to a map document with a python script

I would like to add a topology and its associated layers to a map document with a python script (the script does many things and at the end I want it to load the layers to the mxd). When I try to use

arcpy.MakeFeatureLayer_management (topology_layer,feature_layer)
lyrLayer = arcpy.mapping.Layer(feat_layer)
arcpy.mapping.AddLayer(df,lyrLayer, "TOP")

it says:
ExecuteError: Failed to execute. Parameters are not valid.
ERROR 000732: Input Features: Dataset \\dbs\DBS_ntdisk\tiger10\gdb\geo065.gdb\Tiger10\ed15_topology does not exist or is not supported

What type of layer is the topology? how can I add it to the current mxd?
Thanks!