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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 __mark(self, element, mark_set):
 """ Marks an element :param element: The element to mark :param mark_set: The set corresponding to the mark :return: True if the element was known """

        try:
            # The given element can be of a different type than the original
            # one (JID instead of str, ...), so we retrieve the original one
            original = self.__elements.pop(element)
            mark_set.add(original)
        except KeyError:
            return False
        else:
            if not self.__elements:
                # No more elements to wait for
                self.__call()
            return True