earth = Space('Earth') mars = Space('Mars') solar_system.add_element(mercury) solar_system.add_element(venus) solar_system.add_element(earth) solar_system.add_element(mars) moon = Space('Moon') earth.add_element(moon) lunohod = Space('Lunohod') moon.add_element(lunohod) phobos = Space('Phobos') phobos2 = Space('Phobos') phobos3 = Space('Phobos') deimos = Space('Deimos') mars.add_element(phobos) mars.add_element(phobos2) mars.add_element(phobos3) mars.add_element(deimos) phobos.detach_from_parent() earth.add_element(phobos) phobos.detach_from_parent() mars.add_element(phobos) solar_system.print_tree() mars.remove_element(lunohod) print(phobos2.name)