message: Clarify the docstring that implementations of `tf.data.Dataset` must explicitly set the output parameters.
diff: @@ -647,6 +647,10 @@ class IteratorBase {
  // should be converted to a different error type before being propagated to
  // the caller.
  //
  + // Implementations must explicitly set `*end_of_sequence = false` if an
  + // `Status::OK()` status is returned and the iterator is not at the end of the
  + // sequence.
  + //
  // This method is thread-safe.
  //
  // TODO(mrry): Define `GetNextAsync()` or `GetNextManyAsync()`, and
  @@ -1045,6 +1049,9 @@ class DatasetBaseIterator : public IteratorBase {
  }
  // Internal implementation of GetNext that is wrapped in tracing logic.
  + //
  + // See the docstring of `GetNext` method regaring the contract for
  + // `out_tensors` and `end_of_sequence`.
  virtual Status GetNextInternal(IteratorContext* ctx,
  std::vector<Tensor>* out_tensors,
  bool* end_of_sequence) = 0;
  