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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 truncate(self, size=0):
 """ Truncates the stream to the specified length. @param size: The length of the stream, in bytes. @type size: C{int} """

        if size == 0:
            self._buffer = StringIO()
            self._len_changed = True

            return

        cur_pos = self.tell()
        self.seek(0)
        buf = self.read(size)
        self._buffer = StringIO()

        self._buffer.write(buf)
        self.seek(cur_pos)
        self._len_changed = True