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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 as_set(self, preserve_casing=False):
 """Return the set as real python set type. When calling this, all the items are converted to lowercase and the ordering is lost. :param preserve_casing: if set to `True` the items in the set returned will have the original case like in the :class:`HeaderSet`, otherwise they will be lowercase. """

        if preserve_casing:
            return set(self._headers)
        return set(self._set)