Get the Topological Links between Managed Elements contained within the Subnetwork and their distinguishing information.
For singletons subnetworks, no topologicalLinks will be returned. The EMS should report topological links at the "lowest" layer (i.e. closest to physical) about which it has accurate knowledge.

Operation Exceptions:
1. NOT_IMPLEMENTED - Raised when EMS cannot support this operation.
2. INTERNAL_ERROR - Raised in case of non-specific EMS internal failure.
3. NE_COMM_LOSS - Raised when communication to managed element is lost.
