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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 add_filter(self, label):
 """Add label to FILTER if not set yet, removing ``PASS`` entry if present """

        if label not in self.FILTER:
            if "PASS" in self.FILTER:
                self.FILTER = [f for f in self.FILTER if f != "PASS"]
            self.FILTER.append(label)