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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 add(self, data, id='*', maxlen=None, approximate=True):
 """ Add data to a stream. :param dict data: data to add to stream :param id: identifier for message ('*' to automatically append) :param maxlen: maximum length for stream :param approximate: allow stream max length to be approximate :returns: the added message id. """

        return self.database.xadd(self.key, data, id, maxlen, approximate)