It is possible to create a register with references to the same qubit. This goes through and eliminates duplicate references, leaving the reference at the lowest index.
A reference to the register with the duplicates eliminated.
Assembly: Cove.Base (Module: Cove.Base) Version: 18.104.22.168 (22.214.171.124)
If the register contains qubits ABACDAC then a register containing only ABCD is returned.