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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 query_unique(self, field):
 """Return a list of unique values appearing in the journal for the given `field`. Note this does not respect any journal matches. Entries will be processed with converters specified during Reader creation. """

        return set(self._convert_field(field, value)
                   for value in super(Reader, self).query_unique(field))