error with export_responses function

[piotx]

Traceback (most recent call last):
File "example.py", line 21, in
export_res_token = lime.export_responses(sid, token)
File "/home/p/programming/python/lime-py-api/limesurvey.py", line 126, in export_responses
out = b64decode(self._getJSON(data)['result']).decode('utf-8')
File "/usr/lib/python2.7/base64.py", line 75, in b64decode
return binascii.a2b_base64(s)
TypeError: a2b_base64() argument 1 must be string or buffer, not dict

when I add print self._getJSON(data)['result']) before line 126 in limesruvey.py I get:
{u'status': u'Language code not found for this survey.'}

any ideas, how to fix this