Update constants key to work with v2.1

optuna_dashboard/_serializer.py

@@ -8,7 +8,6 @@ from typing import Union
 import numpy as np
 from optuna.distributions import BaseDistribution
 from optuna.distributions import CategoricalDistribution
-from optuna.samplers._base import _CONSTRAINTS_KEY
 from optuna.study import StudySummary
 from optuna.trial import FrozenTrial
 
@@ -84,6 +83,7 @@ if TYPE_CHECKING:
 
 
 MAX_ATTR_LENGTH = 1024
+CONSTRAINTS_KEY = "constraints"
 
 
 def serialize_attrs(attrs: dict[str, Any]) -> list[Attribute]:
@@ -188,7 +188,7 @@ def serialize_frozen_trial(
         ),
         "note": note.get_note_from_system_attrs(study_system_attrs, trial._trial_id),
         "artifacts": list_trial_artifacts(study_system_attrs, trial._trial_id),
-        "constraints": trial_system_attrs.get(_CONSTRAINTS_KEY, []),
+        "constraints": trial_system_attrs.get(CONSTRAINTS_KEY, []),
     }
 
     serialized_intermediate_values: list[IntermediateValue] = []