code: def create_spot_datafeed_subscription(self, bucket, prefix):
          
          params = {'Bucket' : bucket}
          if prefix:
              params['Prefix'] = prefix
          return self.get_object('CreateSpotDatafeedSubscription',
                                 params, SpotDatafeedSubscription, verb='POST')
docs: Create a spot instance datafeed subscription for this account.
  
          :type bucket: str or unicode
          :param bucket: The name of the bucket where spot instance data
                         will be written.  The account issuing this request
                         must have FULL_CONTROL access to the bucket
                         specified in the request.
  
          :type prefix: str or unicode
          :param prefix: An optional prefix that will be pre-pended to all
                         data files written to the bucket.
  
          :rtype: :class:`boto.ec2.spotdatafeedsubscription.SpotDatafeedSubscription`
          :return: The datafeed subscription object or None