How do I change my symbology in arcpy to have a clear outline point?

I am not sure why my arcpy result's point outline is not changing to clear in ArcGIS Pro. Everything else works, except for the outline syntax. Is there anything wrong with my syntax or this may be a ArcPro bug?

`#Add spatial join layer to the current map
p = arcpy.mp.ArcGISProject('CURRENT')
m = p.listMaps('CompTool')[0]
layer = Stream_Comp.getOutput(0)
m.addDataFromPath(layer)

#Format symbology rendering 
l = m.listLayers(StreamComp_Name)[0]
sym = l.symbology


if sym.renderer.type == 'SimpleRenderer':
    sym.updateRenderer('GraduatedColorsRenderer')
    sym.renderer.classificationField = Comp_Field
    sym.renderer.classificationMethod = 'NaturalBreaks'
    sym.renderer.breakCount = 7


#Updating Symbology Rendering - error:nothing happens to the symbol outline     
for brk in sym.renderer.classBreaks:
    brk.symbol.size = 6
    brk.symbol.outlineColor = {'RGB' : [0, 0, 0, 0]}`