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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 write(self, s):
 """Write the string ``s`` to the pseudoterminal. Returns the number of bytes written. """

        if not self.isalive():
            raise EOFError('Pty is closed')
        if PY2:
            s = _unicode(s)

        success, nbytes = self.pty.write(s)
        if not success:
            raise IOError('Write failed')
        return nbytes