@Override
    public void debug(Throwable error) {
        logger.debug("", error);
    }

    @Override
    public void debug(Supplier<String> content) {
        if (isDebugEnabled()) {
            logger.debug(content.get());
        }
    }

    @Override
    public void debug(Supplier<String> content, Throwable error) {
        if (isDebugEnabled()) {
            logger.debug(content.get(), error);
        }
    }

        public int hashCode() {
            return hash;
        }
    }

    static class CachingSupplier<T> implements Supplier<T> {
        final Supplier<T> supplier;
        volatile Object value;

        CachingSupplier(Supplier<T> supplier) {
            this.supplier = supplier;
        }

        @Override
        @SuppressWarnings({"unchecked", "checkstyle:InnerAssignment"})
        public T get() {

 * memorized and kept as long as supplier instance is kept open.
 * <p>
 * This class is not thread safe and must be used from one thread only, while the constructed {@link RepositorySystem}
 * is thread safe.
 * <p>
 * Important: Given the instance of supplier memorizes the supplier {@link RepositorySystem} instance it supplies,

     * The stack trace for this exception will be output when this error level is enabled.
     *
     * @param error
     */
    void debug(Throwable error);

    void debug(Supplier<String> content);

    void debug(Supplier<String> content, Throwable error);

    /**
     * @return true if the <b>info</b> error level is enabled
     */
    boolean isInfoEnabled();

    /**

                }
            }
            return model;
        }

        public Model computeIfAbsent(Supplier<Model> supplier) {
            if (!set) {
                synchronized (this) {
                    if (!set) {
                        this.set = true;
                        this.model = supplier.get();
                        this.notifyAll();
                    }
                }
            }

    }

    public PluginDescriptor get(Key cacheKey) {
        return clone(descriptors.get(cacheKey));
    }

    @Override
    public PluginDescriptor get(Key key, PluginDescriptorSupplier supplier)
            throws PluginDescriptorParsingException, PluginResolutionException, InvalidPluginDescriptorException {

        try {
            PluginDescriptor desc = descriptors.get(key);
            if (desc == null) {

import org.eclipse.aether.util.repository.SimpleArtifactDescriptorPolicy;

import static java.util.Objects.requireNonNull;

/**
 * A simple {@link Supplier} of {@link SessionBuilder} instances, that on each call supplies newly
 * constructed instance. To create session out of builder, use {@link SessionBuilder#build()}. For proper closing
 * of sessions, use {@link CloseableSession#close()} method on built instance(s).

import java.nio.file.Path;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Supplier;

import org.apache.maven.artifact.DefaultArtifact;
import org.apache.maven.internal.transformation.TransformationFailedException;
import org.apache.maven.model.building.ModelBuildingException;

            @Nullable
            @Override
            @SuppressWarnings("unchecked")
            public <T> T computeIfAbsent(@Nonnull Key<T> key, @Nonnull Supplier<T> supplier) {
                return (T) data.computeIfAbsent(key, (Supplier<Object>) supplier);
            }
        };
    }

    @Nonnull
    @Override
    public LocalRepository getLocalRepository() {

        throw (T) t; // rely on vacuous cast
    }

    static class LazyMap<K, V> extends AbstractMap<K, V> {
        private final Supplier<Map<K, V>> supplier;
        private volatile Map<K, V> delegate;

        LazyMap(Supplier<Map<K, V>> supplier) {
            this.supplier = supplier;
        }

        @Override
        public Set<Entry<K, V>> entrySet() {
            if (delegate == null) {