Fix assignment_helper_QML for new qiskit version

assignment_helper_QML.py

@@ -134,7 +134,7 @@ if __name__ == "__main__":
         from qiskit import QuantumCircuit, ClassicalRegister, QuantumRegister
         from qiskit import execute, BasicAer
         from qiskit.quantum_info import Pauli
-        from qiskit.aqua import Operator, get_aer_backend
+        from qiskit.aqua import get_aer_backend
         from qiskit.aqua.components.initial_states import Custom
         is_qiskit = True
     except ImportError: