this.rootDirectory = rootDirectory;
            return this;
        }

        public ProtoSession build() {
            return new Impl(userProperties, systemProperties, startTime, topDirectory, rootDirectory);
        }

        private static class Impl implements ProtoSession {
            private final Map<String, String> userProperties;
            private final Map<String, String> systemProperties;

    protected List<Path> parseExtClasspath(C context) throws Exception {
        ProtoSession protoSession = context.protoSession;
        String extClassPath = protoSession.getUserProperties().get(Constants.MAVEN_EXT_CLASS_PATH);
        if (extClassPath == null) {
            extClassPath = protoSession.getSystemProperties().get(Constants.MAVEN_EXT_CLASS_PATH);
            if (extClassPath != null) {

     *
     * @param <P> the type of problem
     * @param protoSession the session containing configuration for the problem collector
     * @return a new problem collector instance
     */
    @Nonnull
    static <P extends BuilderProblem> ProblemCollector<P> create(@Nullable ProtoSession protoSession) {
        if (protoSession != null
                && protoSession.getUserProperties().containsKey(Constants.MAVEN_BUILDER_MAX_PROBLEMS)) {

     */
    protected void pushUserProperties(C context) throws Exception {
        ProtoSession protoSession = context.protoSession;
        HashSet<String> sys = new HashSet<>(protoSession.getSystemProperties().keySet());
        if (context.pushedUserProperties == null) {
            context.pushedUserProperties = new HashSet<>();
            protoSession.getUserProperties().entrySet().stream()

                        "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);
            }
        }

import org.apache.maven.api.toolchain.ToolchainModel;

/**
 * The session to install / deploy / resolve artifacts and dependencies.
 *
 * @since 4.0.0
 */
@Experimental
@ThreadSafe
public interface Session extends ProtoSession {

    /**
     * Returns the current maven version.
     *
     * @return the maven version, never {@code null}
     */
    @Nonnull
    Version getMavenVersion();

    /**