public Set<FactIdentifier> getFactIdentifiers() {
        return factMappings.stream().map(FactMapping::getFactIdentifier).collect(Collectors.toSet());
    }
@Test
    public void getFactIdentifiers() {
        modelDescriptor.addFactMapping(factIdentifier, expressionIdentifier);
        
        assertThat(modelDescriptor.getFactIdentifiers()).isNotNull().hasSize(1).containsExactly(factIdentifier);
    }