updates import statement to ensure import of JSONArrowType

Author: chalmerlowe

db_dtypes/__init__.py

@@ -28,7 +28,7 @@
 import pyarrow.compute
 
 from db_dtypes import core
-from db_dtypes.json import JSONArray, JSONDtype
+from db_dtypes.json import JSONArray, JSONDtype, JSONArrowType
 
 from . import _versions_helpers