message: [tf.contrib.bigtable] Switch to returning DatasetV1 instances from API methods.
  This change is necessary before the V1 and V2 interfaces diverge any further.
diff: @@ -222,7 +222,7 @@ class BigtableTable(object):
  A `tf.data.Dataset`. containing `tf.string` Tensors corresponding to all
  of the row keys matching that prefix.
  """
  - return _BigtablePrefixKeyDataset(self, prefix)
  + return dataset_ops.DatasetV1Adapter(_BigtablePrefixKeyDataset(self, prefix))
  def sample_keys(self):
  """Retrieves a sampling of row keys from the Bigtable table.
  @@ -234,7 +234,7 @@ class BigtableTable(object):
  Returns:
  A `tf.data.Dataset` returning string row keys.
  """
  - return _BigtableSampleKeysDataset(self)
  + return dataset_ops.DatasetV1Adapter(_BigtableSampleKeysDataset(self))
  def scan_prefix(self, prefix, probability=None, columns=None, **kwargs):
  """Retrieves row (including values) from the Bigtable service.
  @@ -279,7 +279,8 @@ class BigtableTable(object):
  """
  probability = _normalize_probability(probability)
  normalized = _normalize_columns(columns, kwargs)
  - return _BigtableScanDataset(self, prefix, "", "", normalized, probability)
  + return dataset_ops.DatasetV1Adapter(
  + _BigtableScanDataset(self, prefix, "", "", normalized, probability))
  def scan_range(self, start, end, probability=None, columns=None, **kwargs):
  """Retrieves rows (including values) from the Bigtable service.
  @@ -324,7 +325,8 @@ class BigtableTable(object):
  """
  probability = _normalize_probability(probability)
  normalized = _normalize_columns(columns, kwargs)
  - return _BigtableScanDataset(self, "", start, end, normalized, probability)
  + return dataset_ops.DatasetV1Adapter(
  + _BigtableScanDataset(self, "", start, end, normalized, probability))
  def parallel_scan_prefix(self,
  prefix,
  @@ -380,7 +382,8 @@ class BigtableTable(object):
  """
  probability = _normalize_probability(probability)
  normalized = _normalize_columns(columns, kwargs)
  - ds = _BigtableSampleKeyPairsDataset(self, prefix, "", "")
  + ds = dataset_ops.DatasetV1Adapter(
  + _BigtableSampleKeyPairsDataset(self, prefix, "", ""))
  return self._make_parallel_scan_dataset(ds, num_parallel_scans, probability,
  normalized)
  @@ -442,7 +445,8 @@ class BigtableTable(object):
  """
  probability = _normalize_probability(probability)
  normalized = _normalize_columns(columns, kwargs)
  - ds = _BigtableSampleKeyPairsDataset(self, "", start, end)
  + ds = dataset_ops.DatasetV1Adapter(
  + _BigtableSampleKeyPairsDataset(self, "", start, end))
  return self._make_parallel_scan_dataset(ds, num_parallel_scans, probability,
  normalized)
  