This API is mainly for Terminal Emulator implementors -- any python
program that attempts to determine the printable width of a string on
a Terminal. It is implemented in python (no C library calls) and has
no 3rd-party dependencies.

It is certainly possible to use your Operating System's wcwidth(3)
and wcswidth(3) calls if it is POSIX-conforming, but this would not
be possible on non-POSIX platforms, such as Windows, or for
alternative Python implementations, such as jython. It is also
commonly many releases older than the most current Unicode Standard
release files, which this project aims to track.