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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 update(self, iterable):
 """Add all the headers from the iterable to the set. :param iterable: updates the set with the items from the iterable. """

        inserted_any = False
        for header in iterable:
            key = header.lower()
            if key not in self._set:
                self._headers.append(header)
                self._set.add(key)
                inserted_any = True
        if inserted_any and self.on_update is not None:
            self.on_update(self)