Importing Python module in Jython Stage

I am trying to use Jython Stage to process the JSON data as it is bit complex JSON.

I used below code to import python module but getting error,

Code : 

try:
  sdc.importLock()
  import sys
  sys.path.append('/python/sdc-packages')
  import json_normalize
finally:
  sdc.importUnlock()

 Error :

com.streamsets.pipeline.api.StageException: SCRIPTING_06 - Script error while processing batch: javax.script.ScriptException: ImportError: No module named json_normalize in <script> at line

If you can advise.