Prevent import of Literal for Python < 3.8

src/linkahead/common/datatype.py

@@ -24,7 +24,9 @@
 #
 
 import re
-from typing import Literal
+import sys
+if sys.version_info >= (3, 8):
+    from typing import Literal
 
 from ..exceptions import EmptyUniqueQueryError, QueryNotUniqueError