// Builds a tensor filled with ones with the same shape and dtype as `t`.
  virtual Status BuildOnesLike(const TapeTensor& t,
                               Gradient** result) const = 0;

  // Looks up the ID of a Gradient.
  virtual int64_t TensorId(Gradient* tensor) const = 0;

  // Converts a Gradient to a TapeTensor.
  virtual TapeTensor TapeTensorFromGradient(Gradient* gradient) const = 0;

/// same filesystem and the malicious one loads before the legimitate one -
/// but we consider this to be something that users should care about and
/// manage themselves). In both of these cases, core TensorFlow looks for
/// the `TF_InitPlugin` symbol and calls this function.
///
/// For every filesystem URI scheme that this plugin supports, the plugin must
/// add one `TF_FilesystemPluginInfo` entry in `plugin_info->ops` and call