More 0.32 related fixes (#4520)

* Remove function use that causes hash warning

* Remove MeasurementValueError

* Sphinx fix

* Changed to list comprehension

doc/code/qml_measurements.rst

@@ -15,4 +15,4 @@ qml.measurements
     :no-heading:
     :include-all-objects:
     :inheritance-diagram:
-    :skip: MeasurementShapeError, MeasurementValueError, ObservableReturnTypes
+    :skip: MeasurementShapeError, ObservableReturnTypes

pennylane/measurements/__init__.py

@@ -213,7 +213,7 @@ def circuit(x):
     Variance,
     VnEntropy,
 )
-from .mid_measure import MeasurementValue, MeasurementValueError, MidMeasureMP, measure
+from .mid_measure import MeasurementValue, MidMeasureMP, measure
 from .mutual_info import MutualInfoMP, mutual_info
 from .purity import PurityMP, purity
 from .probs import ProbabilityMP, probs

pennylane/measurements/mid_measure.py

@@ -155,10 +155,6 @@ def hash(self):
         return hash(fingerprint)
 
 
-class MeasurementValueError(ValueError):
-    """Error raised when an unknown measurement value is being used."""
-
-
 class MeasurementValue(Generic[T]):
     """A class representing unknown measurement outcomes in the qubit model.
 

pennylane/optimize/adaptive.py

@@ -188,14 +188,14 @@ def step_and_cost(self, circuit, operator_pool, drain_pool=False, params_zero=Tr
         qnode = copy.copy(circuit)
 
         if drain_pool:
-            repeated_gates = [
+            operator_pool = [
                 gate
                 for gate in operator_pool
-                for operation in circuit.tape.operations
-                if (gate.name == operation.name and gate.wires == operation.wires)
+                if all(
+                    gate.name != operation.name or gate.wires != operation.wires
+                    for operation in circuit.tape.operations
+                )
             ]
-            for gate in repeated_gates:
-                operator_pool.remove(gate)
 
         params = np.array([gate.parameters[0] for gate in operator_pool], requires_grad=True)
         qnode.func = self._circuit