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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 save(self):
 """Saves the instance to the datastore."""

        if not self.is_valid():
            return self._errors
        _new = self.is_new()
        if _new:
            self._initialize_id()
        with Mutex(self):
            self._write(_new)
        return True