Bugfix: Error when uploading some circuits to TorchQuantum #208
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Fixes bug with importing transpiled circuits which are mapped trivially (resulting in a set initial_layout but a null final_layout). This will come up often on circuits that are transpiled with optimization_level=0, though this can happen on any level of optimization if the trivial layout happens to be optimal.
Code to replicate the bug:
`
from torchquantum.plugins import qiskit2tq
from qiskit.circuit.library import RealAmplitudes
from qiskit.compiler import transpile
from qiskit.providers.fake_provider import FakeGuadalupe
backend = FakeGuadalupe()
ansatz = RealAmplitudes(2, reps=1)
ansatz = transpile(ansatz, backend, optimization_level=0)
params = [0]*len(ansatz.parameters)
ansatz = ansatz.bind_parameters(params)
tq_layer = qiskit2tq(ansatz)
`