call_state_.emplace(nullptr, false);
  }

  virtual ~ForwardAccumulator() {
    for (auto accumulated : accumulated_gradients_) {
      vspace_.DeleteGradient(accumulated.second);
    }
  }

  // Tell the forward accumulator to watch tensor_id, with a Tensor tangent
  // vector `tangent` of matching shape and dtype. Tangents are the "vector" in
  // "Jacobian-vector product"; `Watch`ing a new Tensor and immediately calling

  write_to_bazelrc('build --python_path=\"{}"'.format(python_bin_path))
  environ_cp['PYTHON_BIN_PATH'] = python_bin_path

  # If choosen python_lib_path is from a path specified in the PYTHONPATH
  # variable, need to tell bazel to include PYTHONPATH
  if environ_cp.get('PYTHONPATH'):
    python_paths = environ_cp.get('PYTHONPATH').split(':')
    if python_lib_path in python_paths:

# Therefore, "tfrun" commands cannot include pipes -- which is
# probably for the better. If a pipe is necessary for something, it is probably
# complex. Write a well-documented script under utilities/ to encapsulate the
# functionality instead.
tfrun() { "$@"; }

# Run all "tfrun" commands under Docker. See setup_docker.sh for details
if [[ "$TFCI_DOCKER_ENABLE" == 1 ]]; then