util.tensorboard: Fix type annotations requiring Python 3.10+ (now Python 3.9+)

Author: opcode81

CHANGELOG.md

@@ -7,6 +7,10 @@
 * Dropped support for Python versions below 3.9
 * Dropped support for TensorFlow (removing `sensai.tensorflow`)
 
+### Fixes
+
+* `util.tensorboard`: Fix type annotations requiring Python 3.10+ (now Python 3.9+)
+
 ## 1.4.0 (2025-01-21)
 
 ### Improvements/Changes

src/sensai/util/tensorboard.py

@@ -1,3 +1,5 @@
+from typing import List, Optional
+
 import numpy as np
 import pandas as pd
 from tensorboard.backend.event_processing import event_accumulator
@@ -43,15 +45,15 @@ def get_series(self, tag: str, smoothing_factor: float = 0.0) -> pd.Series:
 
         return pd.Series(values, index=steps, name=tag)
 
-    def get_tags(self) -> list[str]:
+    def get_tags(self) -> List[str]:
         """
         Get list of available scalar tags in the events.
 
         :return: list of tag names
         """
         return self.events.Tags()['scalars']
 
-    def get_data_frame(self, tags: list[str] | None = None, smoothing_factor: float = 0.0) -> pd.DataFrame:
+    def get_data_frame(self, tags: Optional[List[str]] = None, smoothing_factor: float = 0.0) -> pd.DataFrame:
         """
         Gets multiple series as a DataFrame.