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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 close (self):
 """Close the file descriptor. Calling this method a second time does nothing, but if the file descriptor was closed elsewhere, :class:`OSError` will be raised. """

        if self.child_fd == -1:
            return

        self.flush()
        os.close(self.child_fd)
        self.child_fd = -1
        self.closed = True