Fix pyre errors in experiment.py (facebook#4179)

Summary:

Fix remaining Pyre errors in experiment.py

Reviewed By: mpolson64, lena-kashtelyan

Differential Revision: D80579073

Author: Cesar-Cardoso

ax/core/experiment.py

@@ -126,8 +126,7 @@ def __init__(
         # pyre-fixme[13]: Attribute `_search_space` is never initialized.
         self._search_space: SearchSpace
         self._status_quo: Arm | None = None
-        # pyre-fixme[13]: Attribute `_is_test` is never initialized.
-        self._is_test: bool
+        self._is_test: bool = False
 
         self._name = name
         self.description = description
@@ -136,14 +135,12 @@ def __init__(
 
         self._data_by_trial: dict[int, OrderedDict[int, Data]] = {}
         self._experiment_type: str | None = experiment_type
-        # pyre-fixme[4]: Attribute must be annotated.
-        self._optimization_config = None
+        self._optimization_config: OptimizationConfig | None = None
         self._tracking_metrics: dict[str, Metric] = {}
         self._time_created: datetime = datetime.now()
         self._trials: dict[int, BaseTrial] = {}
         self._properties: dict[str, Any] = properties or {}
-        # pyre-fixme[4]: Attribute must be annotated.
-        self._default_data_type = default_data_type or DataType.DATA
+        self._default_data_type: DataType = default_data_type or DataType.DATA
         # Used to keep track of whether any trials on the experiment
         # specify a TTL. Since trials need to be checked for their TTL's
         # expiration often, having this attribute helps avoid unnecessary
@@ -402,20 +399,20 @@ def status_quo(self, status_quo: Arm | None) -> None:
         # If old status_quo not present in any trials,
         # remove from _arms_by_signature
         if self._status_quo is not None:
+            old_status_quo_name = self._status_quo.name
+            old_status_quo_signature = self._status_quo.signature
             logger.warning(
                 "Experiment's status_quo is updated. "
                 "Generally the status_quo should not be changed after being set."
             )
             persist_old_sq = False
             for trial in self._trials.values():
-                # pyre-fixme[16]: `Optional` has no attribute `name`.
-                if self._status_quo.name in trial.arms_by_name:
+                if old_status_quo_name in trial.arms_by_name:
                     persist_old_sq = True
                     break
             if not persist_old_sq:
-                # pyre-fixme[16]: `Optional` has no attribute `signature`.
-                self._arms_by_signature.pop(self._status_quo.signature)
-                self._arms_by_name.pop(self._status_quo.name)
+                self._arms_by_signature.pop(old_status_quo_signature)
+                self._arms_by_name.pop(old_status_quo_name)
 
         self._status_quo = status_quo