human
Solve the following python programming problem given the following code:
def convert_header_to_unicode(header) : 
    def _decode(value, encoding) : 
        if isinstance (value, six.text_type) : 
            return value 
if ((not encoding) or (encoding == 'unknown-8bit')) : 
            encoding = DEFAULT_CHARSET 
return value.decode (encoding, 'replace') 
try : 
        return ''.join ([_decode (bytestr, _decode) for (bytestr, encoding) in email.header.decode_header (header)]) 
except UnicodeDecodeError : 
        logger.exception ('Errors encountered decoding header %s into encoding %s.', header, DEFAULT_CHARSET) 
        return unicode (header, DEFAULT_CHARSET, 'replace') 

    
    

    Fix the buggy line: return ''.join ([_decode (bytestr, _decode) for (bytestr, encoding) in email.header.decode_header (header)])
assistant
#Here is Python program to fix the buggy line: return ''.

return ''.join ([_decode (bytestr, encoding) for (bytestr, encoding) in email.header.decode_header (header)])