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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 addUniqueValue(self, value, label, description, symbol):
 """ adds a unique value to the renderer """

        if self._uniqueValueInfos is None:
            self._uniqueValueInfos = []
        self._uniqueValueInfos.append(
            {
                "value" : value,
                "label" : label,
                "description" : description,
                "symbol" : symbol
            }
        )