Use union type instead of union operator

tests/integration/sample.py

@@ -1,13 +1,14 @@
 import logging
 import random
+from typing import Union
 
 logger = logging.getLogger(__name__)
 
 
 def get_sample_granules(
     granules: list,
     sample_size: int,
-    max_granule_size: int | float,
+    max_granule_size: Union[int, float],
     round_ndigits: int = None,
 ):
     """Return a list of randomly-sampled granules and their size in MB.