Thanks for the pull request. I've taken your code and made a few modifications to change it into 85dd6f2.

The changes I've made were mostly for API consistency:

• removed the documentation (normally only generated during release unless something interesting is actually documented)
• changed the module docstring (the first line is used by stdnum.util as one of the steps to update documentation)
• use stdnum.util.clean() to make a compact() function (this does all the right things with all weird values that you can through at it)
• rewrote calc_check_digit() (renamed from calculate_check_digit() to match other modules) to be simpler
• validate() should return a compact representation of the number

Thanks for your contribution.