def append_threshold(data=bpy.data, use_fake_user=False):
    in_sockets = [
        {'default_value': 0.5},
        {'name': 'Lower',
         'default_value': 0.0},
        {'name': 'Upper',
         'default_value': 1.0}
    ]

    out_sockets = [
        {'default_value': 0.5}
    ]

    thresh_group = append_group_node(name='Threshold', data=data, use_fake_user=use_fake_user, in_sockets=in_sockets, out_sockets=out_sockets)

    # Create nodes.
    nodes = thresh_group.nodes
    inbounds = append_group_inst(nodes=nodes, group_name='InBounds', data=data, group_creation_func=append_inbounds, data=data, use_fake_user=use_fake_user)
    mult = append_math_node(nodes, operation='MULTIPLY')

    # Link nodes.
    links = thresh_group.links
    links.new(mult.inputs[0], inbounds.outputs[0])

    # Link to group inputs.
    thresh_input = thresh_group.nodes['Group Input']
    links.new(mult.inputs[1], thresh_input.outputs[0])
    links.new(inbounds.inputs[0], thresh_input.outputs[0])
    links.new(inbounds.inputs[1], thresh_input.outputs[1])
    links.new(inbounds.inputs[2], thresh_input.outputs[2])

    # Link to group outputs.
    thresh_output = thresh_group.nodes['Group Output']
    links.new(thresh_output.inputs[0], mult.outputs[0])