def METHOD_NAME(self, build_number):
    # Returns the best-guess OS version for the build number
    alpha = "abcdefghijklmnopqrstuvwxyz"
    os_version = "Unknown"
    major = minor = ""
    try:
        # Formula looks like this:  AAB; AA - 4 = 10.## version
        # B index in "ABCDEFGHIJKLMNOPQRSTUVXYZ" = 10.##.## version
        split = re.findall(r"[^\W\d_]+|\d+", build_number)
        major = int(split[0])-4
        minor = alpha.index(split[1].lower())
        os_version = "10.{}.{}".format(major, minor)
    except:
        pass
    return os_version