code: def nullify_offsets(offsets):
      
      result = {}
      for topic, partition_offsets in six.iteritems(offsets):
          result[topic] = _nullify_partition_offsets(partition_offsets)
      return result
docs: Modify offsets metadata so that the partition offsets
      have null payloads.
  
      :param offsets: dict {<topic>: {<partition>: <offset>}}
      :returns: a dict topic: partition: offset