ArcPy getDefinition

p = arcpy.mp.ArcGISProject('current')
m=p.activeMap
l=m.listLayers()[0]
l_cim = l.getDefinition('V2')
l_cim.visibility=False
l.setDefinition(l_cim)
hh=m.getDefinition("v2")
hh.spatialReference
{'wkid': 4548, 'latestWkid': 4548}