Save model in ubj as the default. (#9947)

python-package/xgboost/core.py

@@ -2613,7 +2613,7 @@ class Booster:
         else:
             raise TypeError("fname must be a string or os PathLike")
 
-    def save_raw(self, raw_format: str = "deprecated") -> bytearray:
+    def save_raw(self, raw_format: str = "ubj") -> bytearray:
         """Save the model to a in memory buffer representation instead of file.
 
         Parameters

python-package/xgboost/testing/__init__.py

@@ -630,7 +630,7 @@ sparse_datasets_strategy = strategies.sampled_from(
 
 def make_datasets_with_margin(
     unweighted_strategy: strategies.SearchStrategy,
-) -> Callable:
+) -> Callable[[], strategies.SearchStrategy[TestDataset]]:
     """Factory function for creating strategies that generates datasets with weight and
     base margin.
 
@@ -668,8 +668,7 @@ def make_datasets_with_margin(
 
 # A strategy for drawing from a set of example datasets. May add random weights to the
 # dataset
-@memory.cache
-def make_dataset_strategy() -> Callable:
+def make_dataset_strategy() -> strategies.SearchStrategy[TestDataset]:
     _unweighted_datasets_strategy = strategies.sampled_from(
         [
             TestDataset(