def _refresh(self, request):
    body = urllib.urlencode({
      'grant_type': 'refresh_token',
      'client_id': self.client_id,
      'client_secret': self.client_secret,
      'refresh_token' : self.refresh_token
      })
    headers = {
        'user-agent': self.user_agent,
    }

    http_request = atom.http_core.HttpRequest(
        uri=self.token_uri, method='POST', headers=headers)
    http_request.add_body_part(
        body, mime_type='application/x-www-form-urlencoded')
    response = request(http_request)
    body = response.read()
    if response.status == 200:
      self._extract_tokens(body)
    else:
      self._invalid = True
    return response
Refresh the access_token using the refresh_token.
dataset/ETHPy150Open acil-bwh/SlicerCIP/Scripted/attic/PicasaSnap/gdata/gauth.py/OAuth2Token._refresh