int64_t TapeVSpace::NumElements(AbstractTensorHandle* tensor) const {
  // TODO(srbs): It seems like this is used only for performance optimization
  // and not for correctness. The only downside of keeping this 1 seems to be
  // that the gradient accumulation is unbounded and we will never
  // aggressively aggregate accumulated gradients to recover memory.
  // Revisit and fix.
  return 1;
}

      //    internal char array (hard to avoid using StringBuilder)
      // 2. we avoid extra copies into temporary buffers altogether
      // The downside is that this will cause us to store the file bytes in memory twice for a short
      // amount of time.
      return new String(ByteSource.this.read(), charset);
    }

    @Override
    public String toString() {