@Nullable
    @Override
    public Sampler<Class<? extends Throwable>> verboseExceptionSampler() {
        final String spec = getNormalized("verboseExceptions");
        if (spec == null) {
            return null;
        }
        try {
            Sampler.of(spec);
        } catch (Exception e) {
            // Invalid sampler specification
            throw new IllegalArgumentException("invalid sampler spec: " + spec, e);
        }
        return new ExceptionSampler(spec);
    }
Implementation of {@link FlagsProvider} which provides values from JVM options to {@link Flags}.
core/src/main/java/com/linecorp/armeria/common/SystemPropertyFlagsProvider.java