Fix VQE runtime ValueError (#182)

* Small change.

* Update location.

* Run black.

* Update.

* Change init.

* Black.

* Update import

* Blank line.

* Update.

* Update.

* Update.

* Update path.

* Change dic

* Update pennylane_qiskit/vqe_runtime_runner.py

pennylane_qiskit/vqe_runtime_runner.py

@@ -73,12 +73,14 @@ def _callback(self, *args):
             step (float): Value of the step.
             accepted (bool): True if the loss function value has improved, False otherwise.
         """
-        _, (nfev, xk, fk, step, accepted) = args
-        self.intermediate_results["nfev"].append(nfev)
-        self.intermediate_results["parameters"].append(xk)
-        self.intermediate_results["function"].append(fk)
-        self.intermediate_results["step"].append(step)
-        self.intermediate_results["accepted"].append(accepted)
+        # If it is a dictionary it is the final result and does not belong to intermediate results
+        if not isinstance(args[1], dict):
+            _, (nfev, xk, fk, step, accepted) = args
+            self.intermediate_results["nfev"].append(nfev)
+            self.intermediate_results["parameters"].append(xk)
+            self.intermediate_results["function"].append(fk)
+            self.intermediate_results["step"].append(step)
+            self.intermediate_results["accepted"].append(accepted)
 
     def _scipy_callback(self, *args):
         """The callback function that attaches intermediate results to the wrapper: