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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 _format_value(self, value):
 """ Return formatted string """

        value, unit = self.py3.format_units(value, unit=self.unit, si=self.si_units)
        return self.py3.safe_format(self.format_value, {"value": value, "unit": unit})