code: def add_bucket(self, bucket, bucket_type=None):
          
          if not riak.disable_list_exceptions:
              raise riak.ListError()
          self._input_mode = 'bucket'
          if isinstance(bucket, riak.RiakBucket):
              if bucket.bucket_type.is_default():
                  self._inputs = {'bucket': bucket.name}
              else:
                  self._inputs = {'bucket': [bucket.bucket_type.name,
                                             bucket.name]}
          elif bucket_type is not None and bucket_type != "default":
              self._inputs = {'bucket': [bucket_type, bucket]}
          else:
              self._inputs = {'bucket': bucket}
          return self
docs: Adds all keys in a bucket to the inputs.
  
          :param bucket: the bucket
          :type bucket: string
          :param bucket_type: Optional name of a bucket type
          :type bucket_type: string, None
          :rtype: :class:`RiakMapReduce`