SparsePauliOp' object has no attribute 'primitive_strings' warning for a max-cut problem using QAOA and MinimuEigenOptimizer

Question

I am using Qiskit to implement QAOA for a max-cut problem. I am using inbuilt qiskit implemetation of QAOA and, the MinimuEigenOptimizer. The MinimuEigenOptimizer.solve() throws the warning.

AttributeError: 'SparsePauliOp' object has no attribute 'primitive_strings'

I am new to Qiskit, any help will be appreciated!

Below is the code:

from qiskit.algorithms import QAOA
from qiskit_optimization.algorithms import MinimumEigenOptimizer
backend = Aer.get_backend('statevector_simulator')
qaoa = QAOA(optimizer = ADAM(), quantum_instance = backend, reps=1, initial_point=[0.1,0.1])
eigen_optimizer = MinimumEigenOptimizer(min_eigen_solver = qaoa)
quadratic_program = quadratic_program_from_graph(graphs['custom'])
result = eigen_optimizer.solve(quadratic_program)
print(result)

the deprecation warning: The class qiskit.algorithms.minimum_eigen_solvers.qaoa.QAOA is deprecated as of qiskit-terra 0.24.0. It will be removed no earlier than 3 months after the release date. Instead, use the class qiskit.algorithms.minimum_eigensolvers.QAOA. See https://qisk.it/algo_migration for a migration guide.

and the warning:

AttributeError                            Traceback (most recent call last) 
Cell In[59], line 7
      5 eigen_optimizer = MinimumEigenOptimizer(min_eigen_solver = qaoa)
      6 quadratic_program = quadratic_program_from_graph(graphs['custom'])
----> 7 result = eigen_optimizer.solve(quadratic_program)
      8 print(result)

File ~\anaconda3\envs\QAlgobase\Lib\site-  packages\qiskit_optimization\algorithms\minimum_eigen_optimizer.py:205, in     MinimumEigenOptimizer.solve(self, problem)
    202 # construct operator and offset
    203 operator, offset = problem_.to_ising()
--> 205 return self._solve_internal(operator, offset, problem_, problem)

File ~\anaconda3\envs\QAlgobase\Lib\site-packages\qiskit_optimization\algorithms\minimum_eigen_optimizer.py:218, in MinimumEigenOptimizer._solve_internal(self, operator, offset, converted_problem, original_problem)
    215 eigen_result: Optional[MinimumEigensolverResult] = None
    216 if operator.num_qubits > 0:
    217     # approximate ground state of operator using min eigen solver
--> 218     eigen_result = self._min_eigen_solver.compute_minimum_eigenvalue(operator)
    219     # analyze results
    220     raw_samples = None

File ~\anaconda3\envs\QAlgobase\Lib\site-packages\qiskit\algorithms\minimum_eigen_solvers\vqe.py:536, in VQE.compute_minimum_eigenvalue(self, operator, aux_operators)
    533     gradient = self._gradient
    535 self._eval_count = 0
--> 536 energy_evaluation, expectation = self.get_energy_evaluation(
    537     operator, return_expectation=True
    538 )
    540 start_time = time()
    542 if callable(self.optimizer):

File ~\anaconda3\envs\QAlgobase\Lib\site-packages\qiskit\algorithms\minimum_eigen_solvers\vqe.py:613, in VQE.get_energy_evaluation(self, operator, return_expectation)
    610     raise RuntimeError("The ansatz must be parameterized, but has 0 free parameters.")
    612 ansatz_params = self.ansatz.parameters
--> 613 expect_op, expectation = self.construct_expectation(
    614     ansatz_params, operator, return_expectation=True
    615 )
    617 def energy_evaluation(parameters):
    618     parameter_sets = np.reshape(parameters, (-1, num_parameters))

File ~\anaconda3\envs\QAlgobase\Lib\site-packages\qiskit\algorithms\minimum_eigen_solvers\vqe.py:431, in VQE.construct_expectation(self, parameter, operator, return_expectation)
    429 # if expectation was never created, try to create one
    430 if self.expectation is None:
--> 431     expectation = ExpectationFactory.build(
    432         operator=operator,
    433         backend=self.quantum_instance,
    434         include_custom=self._include_custom,
    435     )
    436 else:
    437     expectation = self.expectation

File ~\anaconda3\envs\QAlgobase\Lib\site-packages\qiskit\utils\deprecation.py:96, in deprecate_func.<locals>.decorator.<locals>.wrapper(*args, **kwargs)
     93 @functools.wraps(func)
     94 def wrapper(*args, **kwargs):
     95     warnings.warn(msg, category=category, stacklevel=2)
---> 96     return func(*args, **kwargs)

File ~\anaconda3\envs\QAlgobase\Lib\site-packages\qiskit\opflow\expectations\expectation_factory.py:74, in ExpectationFactory.build(operator, backend, include_custom)
     71 backend_to_check = backend.backend if isinstance(backend, QuantumInstance) else backend
     73 # pylint: disable=cyclic-import
---> 74 primitives = operator.primitive_strings()
     75 if primitives in ({"Pauli"}, {"SparsePauliOp"}):
     77     if backend_to_check is None:
     78         # If user has Aer but didn't specify a backend, use the Aer fast expectation

AttributeError: 'SparsePauliOp' object has no attribute 'primitive_strings' '''