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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 to_string(self, value):
 """ Return a JSON serialized string representation of the value. """

        self._warn_deprecated_outside_JSONField()
        value = json.dumps(
            self.to_json(value),
            indent=2,
            sort_keys=True,
            separators=(',', ': '),
        )
        return value