Update candidate_generation.py

Author: cthoyt

scispacy/candidate_generation.py

@@ -1,4 +1,4 @@
-from typing import Optional, List, Dict, Tuple, NamedTuple, Type
+from typing import Optional, List, Dict, Tuple, NamedTuple, Type, Union
 import json
 import datetime
 import os.path
@@ -44,7 +44,7 @@ class LinkerPaths(NamedTuple):
     concept_aliases_list: str
 
     @classmethod
-    def from_directory(cls, directory: str | Path) -> Self:
+    def from_directory(cls, directory: Union[str, Path]) -> Self:
         if not os.path.isdir(directory):
             raise NotADirectoryError
         return cls(