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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 relabel(self, catalogue):
 """Relabels results rows according to `catalogue`. A row whose work is labelled in the catalogue will have its label set to the label in the catalogue. Rows whose works are not labelled in the catalogue will be unchanged. :param catalogue: mapping of work names to labels :type catalogue: `Catalogue` """

        for work, label in catalogue.items():
            self._matches.loc[self._matches[constants.WORK_FIELDNAME] == work,
                              constants.LABEL_FIELDNAME] = label