def cover(self, match_set):
assert isinstance(match_set, MatchSet)<EOL>assert match_set.model.algorithm is self<EOL>condition = bitstrings.BitCondition.cover(<EOL>match_set.situation,<EOL>self.wildcard_probability<EOL>)<EOL>action_candidates = (<EOL>frozenset(match_set.model.possible_actions) -<EOL>frozenset(match_set)<EOL>)<EOL>if not action_candidates:<EOL><INDENT>action_candidates = match_set.model.possible_actions<EOL><DEDENT>action = random.choice(list(action_candidates))<EOL>return XCSClassifierRule(<EOL>condition,<EOL>action,<EOL>self,<EOL>match_set.time_stamp<EOL>)<EOL>
Return a new classifier rule that can be added to the match set,
        with a condition that matches the situation of the match set and an
        action selected to avoid duplication of the actions already
        contained therein. The match_set argument is a MatchSet instance
        representing the match set to which the returned rule may be added.

        Usage:
            match_set = model.match(situation)
            if model.algorithm.covering_is_required(match_set):
                new_rule = model.algorithm.cover(match_set)
                assert new_rule.condition(situation)
                model.add(new_rule)
                match_set = model.match(situation)

        Arguments:
            match_set: A MatchSet instance.
        Return:
            A new ClassifierRule instance, appropriate for the addition to
            match_set and to the classifier set from which match_set was
            drawn.