:sig
DValue DValue::pop()

:params
return value : removed child, or an empty DValue when no child exists

:see
0_DValue
2_DValue_push

:content
Ensures the value is map-shaped, removes the last entry according to `std::map` reverse key order, and returns it. For list-mode values, the next array index is reset to the new size.

```cpp
DValue last = items.pop();
```