def METHOD_NAME(self) -> Set["MaterialNode"]:
    """Get the active materials for all extruders. No duplicates will be returned"""
    global_stack = cura.CuraApplication.CuraApplication.getInstance().getGlobalContainerStack()
    if global_stack is None:
        return set()
    container_tree = ContainerTree.getInstance()
    machine_node = container_tree.machines[global_stack.definition.getId()]
    nodes = set()  # type: Set[MaterialNode]
    for extruder in global_stack.extruderList:
        active_variant_name = extruder.variant.getMetaDataEntry("name")
        if active_variant_name not in machine_node.variants:
            Logger.log("w", "Could not find the variant %s", active_variant_name)
            continue
        active_variant_node = machine_node.variants[active_variant_name]
        active_material_node = active_variant_node.materials.get(extruder.material.getMetaDataEntry("base_file"))
        if active_material_node is None:
            Logger.log("w", "Could not find the material %s", extruder.material.getMetaDataEntry("base_file"))
            continue
        nodes.add(active_material_node)
    return nodes