Converting text containing COMBINING DIAERESIS to utf-8

We hav some text containing german umlauts repr开发者_开发技巧esented using e.g. 'a' + COMBINING DIAERESIS ($cc $88).

Any idea how to convert such text properly to utf8?

First, if it's not already a unicode then decode it. Second, unicodedata.normalize(). Third, encode.