Python: 2.4
Module: email.Header
Method: encode()
In some cases returns unicode (example on line 5)

1>> from email.Header import Header

2>> Header(unicode('abcá','iso-8859-2'),'utf-8').encode()
'=?utf-8?b?YWJjw6E=?='

3>> Header('abc','utf-8').encode()
'=?utf-8?q?abc?='

4>> Header(u'abc','utf-8').encode()
'abc' ???

5>> Header('abc','iso-8859-2').encode()
u'=?iso-8859-2?q?abc?=' (P2.4)

6>> Header('abc','iso-8859-2').encode()
'=?iso-8859-2?q?abc?=' (P2.3)