*/
    @Nonnull
    Map<String, String> getSystemProperties();

    /**
     * Returns the properly overlaid map of properties: system + user.
     */
    @Nonnull
    Map<String, String> getEffectiveProperties();

    /**
     * Returns the start time of the session.
     *
     * @return the start time as an Instant object, never {@code null}
     */
    @Nonnull
    Instant getStartTime();

    /**

        return Collections.unmodifiableMap(new PropertiesAsMap(getMavenSession().getSystemProperties()));
    }

    @Nonnull
    @Override
    public Map<String, String> getEffectiveProperties(@Nullable Project project) {
        HashMap<String, String> result = new HashMap<>(getSystemProperties());
        if (project != null) {
            result.putAll(project.getModel().getProperties());
        }

    /**
     * Default implementation at {@link ProtoSession} level, as the notion of project
     * does not exist there.
     */
    @Nonnull
    default Map<String, String> getEffectiveProperties() {
        return getEffectiveProperties(null);
    }

    /**
     * Each invocation computes a new map of effective properties. To be used in interpolation.
     * <p>

        // user override
        String userDefinedLocalRepo =
                context.protoSession.getEffectiveProperties().get(Constants.MAVEN_REPO_LOCAL);
        if (userDefinedLocalRepo == null) {
            userDefinedLocalRepo = context.protoSession.getEffectiveProperties().get(Constants.MAVEN_REPO_LOCAL);
            if (userDefinedLocalRepo != null) {

        container.setLoggerManager(createLoggerManager());
        ProtoSession protoSession = context.protoSession;
        UnaryOperator<String> extensionSource = protoSession.getEffectiveProperties()::get;
        List<Throwable> failures = new ArrayList<>();
        for (LoadedCoreExtension extension : loadedExtensions) {
            container.discoverComponents(

                        "The specified user toolchains file does not exist: " + userToolchainsFile);
            }
        } else {
            String userToolchainsFileStr =
                    context.protoSession.getEffectiveProperties().get(Constants.MAVEN_USER_TOOLCHAINS);
            if (userToolchainsFileStr != null) {
                userToolchainsFile = context.cwd.resolve(userToolchainsFileStr);
            }
        }