Where's the at::empty() source code?

I just find

Tensor empty(
    IntArrayRef size,
    c10::optional<DimnameList> names,
    c10::optional<ScalarType> dtype,
    c10::optional<Layout> layout,
    c10::optional<Device> device,
    c10::optional<bool> pin_memory,
    optional<MemoryFormat> optional_memory_format) {
  // See [Note: hacky wrapper removal for TensorOptions]
  TensorOptions options = TensorOptions().dtype(dtype).layout(layout).device(device).pinned_memory(pin_memory);

  if (!names.has_value()) {
    return at::empty(size, options, optional_memory_format);
  }
  TORCH_CHECK(options.layout() == Layout::Strided,
      "NYI: named tensors only support strided layout");
  TORCH_CHECK(options.device().is_cpu() || options.device().is_cuda(),
      "NYI: named tensors only support CPU and CUDA tensors");
  auto result = at::empty(size, options, optional_memory_format);
  internal_set_names_inplace(result, names);
  return result;
}

but then there is nothing about at::empty(size, options, optional_memory_format);