For ArcGIS Pro:
Create an empty group layer and save it, then run this:
empty_group_layer_file = arcpy.mp.LayerFile(r"H:\New Group Layer.lyrx")
active_map = arcpy.mp.ArcGISProject("current").activeMap
# In this example, I'll use a dict of {group_layer_name: [layers]} as input. Adjust according to your existing code.
group_layers = {
"Group Layer 1": [layer_1, layer_2],
"Group Layer 2": [layer_3, layer_4],
}
for group_name, layers in group_layers.items():
group = active_map.addLayer(empty_group_layer_file)[0]
group.name = group_name
for lyr in layers:
active_map.addLayerToGroup(group, lyr)
Have a great day!
Johannes