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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 explainParam(self, param):
 """ Explains a single param and returns its name, doc, and optional default value and user-supplied value in a string. """

        param = self._resolveParam(param)
        values = []
        if self.isDefined(param):
            if param in self._defaultParamMap:
                values.append("default: %s" % self._defaultParamMap[param])
            if param in self._paramMap:
                values.append("current: %s" % self._paramMap[param])
        else:
            values.append("undefined")
        valueStr = "(" + ", ".join(values) + ")"
        return "%s: %s %s" % (param.name, param.doc, valueStr)