There is a global class, Registry, which keep tracks of every important objects created in the emulation (nodes, layers, networks, files, etc.). In fact, what compiles do is just takes the node and network objects out from the Registry and convert them to dockerfiles.
Most of the objects created in the emulator are derived from the Printable
class. As the name suggested, they can be printed. To see what classes are
printable, check the API documentation. Registry is also a printable object,
we can print it to check almost all objects created in the emulation:
print(emu.getRegistry())