An attempt to Enable Symbol Layer Drawing with arcpy

[nsidaniel]

As part of larger process I'm trying to Enable Symbol Layer Drawing. 

1. I tried using the CIM through the Layer class, which didn't work (I may have set it up wrong) and I foolishly deleted my code out of annoyance. 

2. I also tried using the renderer (without the CIM):

sym = lyr.symbology 
sym.updateRenderer('UniqueValueRenderer') 
sym.renderer.enableSymbolLayerDrawing = True
lyr.symbology = sym 

3. Here's my full code currently:

import arcpy

aprx = arcpy.mp.ArcGISProject("CURRENT")
m = aprx.listMaps(map_name)[0]
lyr = m.listLayers(layer_name)[0]
cim_lyr = lyr.getDefinition("V3")

for lblClass in cim_lyr.labelClasses:
    lblClass.expressionEngine = "VBScript"
    lblClass.expression = '"<FNT name=\'Arial\' style=\'Bold\' size=\'8\'><CLR red=\'255\' green=\'255\' blue=\'255\'>" & [ParcelID] & vbNewLine & [OpCo] & " " & [TypeOfUse] & "</CLR></FNT>"'

    if not lblClass.maplexLabelPlacementProperties:
        lblClass.maplexLabelPlacementProperties = arcpy.cim.CreateCIMObjectFromClassName('CIMMaplexLabelPlacementProperties', 'V3')

    lblClass.maplexLabelPlacementProperties.polygonFeatureType = "LandParcel"
    lblClass.maplexLabelPlacementProperties.polygonPlacementMethod = "StraightInPolygon"
    lblClass.maplexLabelPlacementProperties.preferHorizontalPlacement = True
    lblClass.maplexLabelPlacementProperties.multiPartOption = "OneLabelPerPart"
    
    lblClass.maplexLabelPlacementProperties.featureWeight = 0
    lblClass.maplexLabelPlacementProperties.labelWeight = 0 
    lblClass.maplexLabelPlacementProperties.polygonBoundaryWeight = 0
    lblClass.maplexLabelPlacementProperties.avoidOverlappingLabeledPolygonsAsIfHoles = True
    lblClass.maplexLabelPlacementProperties.canRemoveOverlappingLabel = False
    lblClass.maplexLabelPlacementProperties.canPlaceLabelOnTopOfFeature = True
    lblClass.maplexLabelPlacementProperties.canOverrunFeature = True
    lblClass.maplexLabelPlacementProperties.canPlaceLabelOutsidePolygon = False
    lblClass.maplexLabelPlacementProperties.backgroundLabel = True

    lblClass.visibility = True
    lblClass.priority = 0 

sym = lyr.symbology
sym.renderer.enableSymbolLayerDrawing = True

lyr.showLabels = True
m.enableMaplex = True

lyr.symbology = sym
lyr.setDefinition(cim_lyr)
print(f" Label settings updated for {layer_name}")

Any ideas or thoughts are appreciated!

- Daniel