  Here is an example of Python code that sets up a simulation using the dd4hep library:
```
import dd4hep

def display_help():
    print("Usage: python simulation.py [options]")
    print("Options:")
    print("  -h, --help                  Show this help message and exit")
    print("  -g, --geometry <geometry>   Set the geometry to use (default: 'dd4hep')")
    print("  -m, --magnetic-field <field> Set the magnetic field to use (default: 'dd4hep')")
    print("  -p, --particles <particles>  Set the particles to simulate (default: 'all')")
    print("  -d, --detectors <detectors>  Set the detectors to use (default: 'all')")
    print("  -v, --visualize              Enable visualization (default: False)")

def main():
    # Parse command line arguments
    args = CommandLine.parse_args()

    # Set up the logger
    logger = dd4hep.Logger.get_logger()

    # Set up the Geant4 kernel and detector description
    kernel = dd4hep.Kernel.get_kernel()
    detector = dd4hep.Detector.get_detector()

    # Configure the user interface
    ui = dd4hep.UserInterface.get_ui()

    # Load the geometry
    geometry = dd4hep.Geometry.get_geometry(args.geometry)

    # Set up the magnetic field tracking
    magnetic_field = dd4hep.MagneticField.get_magnetic_field(args.magnetic_field)

    # Set up the random generator
    random_generator = dd4hep.RandomGenerator.get_random_generator()

    # Set up the event actions
    event_actions = dd4hep.EventActions.get_event_actions()

    # Set up the I/O
    io = dd4hep.IO.get_io()

    # Set up the various generator actions
    generator_actions = dd4hep.GeneratorActions.get_generator_actions()

    # Set up the simulation particles
    particles = dd4hep.Particles.get_particles(args.particles)

    # Set up the detectors
    detectors = dd4hep.Detectors.get_detectors(args.detectors)

    # Build the physics list
    physics_list = dd4hep.PhysicsList.get_physics_list()

    # Add special particle types
    physics_list.add_special_particle_types()

    # Set a global range cut
    physics_list.set_global_range_cut(1000)

    # If visualization is enabled, set up the visualization
    if args.visualize:
        visualization = dd4hep.Visualization.get_visualization()
        visualization.set_geometry(geometry)
        visualization.set_detectors(detectors)
        visualization.set_particles(particles)
        visualization.set_physics_list(physics_list)

    # Configure, initialize, run, and terminate the kernel
    kernel.configure(geometry, magnetic_field, random_generator, event_actions, io, generator_actions, particles, detectors, physics_list)
    kernel.initialize()
    kernel.run()
    kernel.terminate()

if __name__ == "__main__":
    main()
```
This code sets up a simulation using the dd4hep library, including setting up the logger, parsing command line arguments, setting up the Geant4 kernel and detector description, configuring the user interface, loading a specific geometry, setting up the magnetic field tracking, random generator, event actions, I/O, and various generator actions. The code also handles simulation particles, setup detectors, build the physics list, add special particle types and a global range cut. If visualization is enabled, the code sets up the visualization. Finally, the code configures, initializes, runs, and terminates the kernel.