return absl::OkStatus();
  }

  // We may need to allocate zero inputs for trainable dtypes we don't have JVPs
  // for. Make sure they get cleaned up.
  std::vector<Gradient*> new_zeros;
  auto delete_new_zeros = gtl::MakeCleanup([&new_zeros, this] {
    for (Gradient* tensor : new_zeros) {
      this->vspace_.DeleteGradient(tensor);
    }
  });
  std::vector<Gradient*> in_grads;

		if _, err := io.ReadFull(tr.r, tr.blk[:]); err != nil {
			return nil, nil, err // EOF is okay here; exactly 1 block of zeros read
		}
		if bytes.Equal(tr.blk[:], zeroBlock[:]) {
			return nil, nil, io.EOF // normal EOF; exactly 2 block of zeros read
		}
		return nil, nil, ErrHeader // Zero block and then non-zero block
	}

	// Verify the header matches a known format.
	format := tr.blk.getFormat()

			got := string(readBuf[:n])
			if err != nil || got != want {
				t.Errorf("off %d, size %d = %v, %v (%q); want %q", off, size, n, err, got, want)
			}
		}
	}

}

type zeros struct{}

func (zeros) Read(p []byte) (int, error) {
	clear(p)
	return len(p), nil

					if err := json.Unmarshal(buf.Bytes(), &ei); err == nil && ei.V2Obj != nil {
						verID := uuid.UUID(header.VersionID).String()
						if verID == "00000000-0000-0000-0000-000000000000" {
							// If the version ID is all zeros, use the signature as version ID.
							verID = fmt.Sprintf("null/%08x", header.Signature)
							v0 = verID
						}
						idx := ei.V2Obj.EcIndex

	pr, pw := io.Pipe()
	// Copy input to compressor
	opts := compressOpts
	if encrypted {
		// The values used for padding are not a security concern,
		// but we choose pseudo-random numbers instead of just zeros.
		rng := rand.New(rand.NewSource(time.Now().UnixNano()))
		opts = append([]s2.WriterOption{s2.WriterPadding(compPadEncrypted), s2.WriterPaddingSrc(rng)}, compressOpts...)
	}
	comp := s2.NewWriter(pw, opts...)

   * first decrementing to zero, and then removing. putIfAbsent or replace could observe the
   * intermediate zero-state. Ways we could deal with this are:
   *
   * - Don't define any of the ConcurrentMap operations. This is the current state of affairs.
   *
   * - Define putIfAbsent and replace as treating zero and absent identically (as currently

   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
   * returned, containing the values of {@code array}, and zeroes in the remaining places.
   *
   * @param array the source array
   * @param minLength the minimum length the returned array must guarantee
   * @param padding an extra amount to "grow" the array by if growth is necessary

// iota is a predeclared identifier representing the untyped integer ordinal
// number of the current const specification in a (usually parenthesized)
// const declaration. It is zero-indexed.
const iota = 0 // Untyped int.

// nil is a predeclared identifier representing the zero value for a
// pointer, channel, func, interface, map, or slice type.
var nil Type // Type must be a pointer, channel, func, interface, map, or slice type

   * it is returned directly. Otherwise, a new array of size {@code minLength + padding} is
   * returned, containing the values of {@code array}, and zeroes in the remaining places.
   *
   * @param array the source array
   * @param minLength the minimum length the returned array must guarantee
   * @param padding an extra amount to "grow" the array by if growth is necessary

		pool: sync.Pool{
			New: func() interface{} {
				var t T
				return &t
			},
		},
		emptySz: sz,
	}
}

func (p *JSONPool[T]) new() *T {
	var zero T
	t := p.pool.Get().(*T)
	*t = zero
	return t
}

// JSON is a wrapper around a T object that can be serialized.
// There is an internal value
type JSON[T any] struct {
	p   *JSONPool[T]
	val *T
}