experiments and candidates can be None

bofire/strategies/predictives/botorch.py

@@ -278,6 +278,8 @@ def _ask(self, candidate_count: int) -> pd.DataFrame:
         """
 
         assert candidate_count > 0, "candidate_count has to be larger than zero."
+        if self.experiments is None:
+            raise ValueError("No experiments have been provided yet.")
 
         acqfs = self._get_acqfs(candidate_count)
 

bofire/strategies/strategy.py

@@ -32,22 +32,22 @@ def from_spec(cls, data_model: DataModel) -> "Strategy":
         return cls(data_model=data_model)
 
     @property
-    def experiments(self) -> pd.DataFrame:
+    def experiments(self) -> Optional[pd.DataFrame]:
         """Returns the experiments of the strategy.
 
         Returns:
             pd.DataFrame: Current experiments.
         """
-        return self._experiments  # type: ignore
+        return self._experiments
 
     @property
-    def candidates(self) -> pd.DataFrame:
+    def candidates(self) -> Optional[pd.DataFrame]:
         """Returns the (pending) candidates of the strategy.
 
         Returns:
             pd.DataFrame: Pending experiments.
         """
-        return self._candidates  # type: ignore
+        return self._candidates
 
     def tell(
         self,