Returns a string that can be used with the codecs python package
        to encode or decode the files in the chm archive. If an error is
        found, or if it is not possible to find the encoding, None is
        returned.

def GetEncoding(self):
        '''Returns a string that can be used with the codecs python package
        to encode or decode the files in the chm archive. If an error is
        found, or if it is not possible to find the encoding, None is
        returned.'''
        if self.encoding:
            vals = string.split(self.encoding, ',')
            if len(vals) > 2:
                try:
                    return charset_table[int(vals[2])]
                except KeyError:
                    pass
        return None