The native BMap library file should be placed with `bmap.py` file.
The native BMap library must be named as `BMap.dll` (in Windows), `BMap.so` (in Linux or BSD), `BMap.dylib` (in macOS), or `BMap.bin` (in any other platforms).
If you are building final distributed package file, such as `.whl` file, you may need manually put native BMap library file into package file because I have not write this behavior in any script.