Find a way to initialize field that has in-header initialization

```cpp
// source.cpp
namespace chimera_test {
struct Dog {
  std::string name = "noname";
}
} // chimera_test
```
```cpp
// binding.cpp
m.def_readwrite("format", &chimera_test::Dog::format)
```
`name` is not initialized with `"noname"`.
```python
>>> d = Dog()
>>> print(d.name)
''  # expectation is 'noname'
```