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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 size(self):
 """Return the size of the stream, or -1 if it cannot be determined. """

        pos = self._stream.tell()
        # seek to the end of the stream
        self._stream.seek(0,2)
        size = self._stream.tell()
        self._stream.seek(pos, 0)

        return size