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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 stderr_file(self):

 """Filename to save kernel stderr output."""

        stderr_file = None
        if self.connection_file is not None:
            stderr_file = self.kernel_id + '.stderr'
            if self.stderr_dir is not None:
                stderr_file = osp.join(self.stderr_dir, stderr_file)
            else:
                try:
                    stderr_file = osp.join(get_temp_dir(), stderr_file)
                except (IOError, OSError):
                    stderr_file = None
        return stderr_file