class SetMandatoryFieldImplementer implements RuleActionValidator {

    @Override
    public Map<String, List<String>> validateEvents( TrackerBundle bundle )
    {
        Map<String, List<RuleEffect>> effects = getEffects( bundle.getEventRuleEffects() );

        return effects.entrySet().stream()
            .collect( Collectors.toMap( e -> e.getKey(),
                e -> getEvent( bundle, e.getKey() )
                    .map( tei -> checkMandatoryDataElement( tei, e.getValue() ) ).orElse( Lists.newArrayList() ) ) );
    }

}