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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def unicode(self, s, encoding=None):
 """ Convert a string to unicode using the given encoding, and return it. This function uses the underlying to_unicode attribute. Arguments: s: a basestring instance to convert to unicode. Unlike Python's built-in unicode() function, it is okay to pass unicode strings to this function. (Passing a unicode string to Python's unicode() with the encoding argument throws the error, "TypeError: decoding Unicode is not supported.") encoding: the encoding to pass to the to_unicode attribute. Defaults to None. """

        if isinstance(s, unicode):
            return unicode(s)

        return self.to_unicode(s, encoding)