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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 to_header(self):
 """Convert the etags set into a HTTP header string."""

        if self.star_tag:
            return "*"
        return ", ".join(
            ['"%s"' % x for x in self._strong] + ['W/"%s"' % x for x in self._weak]
        )