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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 _EnsureFileExists(self):
 """Touches a file; returns False on error, True on success."""

        if not os.path.exists(self._filename):
            old_umask = os.umask(0o177)
            try:
                open(self._filename, 'a+b').close()
            except OSError:
                return False
            finally:
                os.umask(old_umask)
        return True