class_docstr: A sliced view for :class:`SliceableDataset`.
class_docstr_tok: ["A","sliced","view","for",":","class",":","`","SliceableDataset","`","."]
code: def keys(self):
      keys = _as_tuple(self._dataset.keys)
      if isinstance(self._key_indices, tuple):
          return tuple(
              keys[key_index] for key_index in self._key_indices
          )
      else:
          return keys[self._key_indices]
  
imports: import numbers
  import numpy
  import six
  import chainer
label_desc: Use image node_id 3 for calling the SlicedDataset obj's underlying member method code with example usage: obj.keys() and returns: tuple, keys