*/
package okhttp3

import okio.IOException

interface Callback {
  /**
   * Called when the request could not be executed due to cancellation, a connectivity problem or
   * timeout. Because networks can fail during an exchange, it is possible that the remote server
   * accepted the request before the failure.
   */
  fun onFailure(
    call: Call,
    e: IOException,
  )

  /**

import org.jspecify.annotations.Nullable;

/**
 * A class to represent the set of edges connecting an (implicit) origin node to a target node.
 *
 * <p>The {@link #nodeToOutEdge} map means this class only works on networks without parallel edges.
 * See {@link MultiEdgesConnecting} for a class that works with parallel edges.
 *
 * @author James Sexton
 * @param <E> Edge parameter type
 */

import java.util.Set;

/**
 * Optional features of classes derived from {@code Set}.
 *
 * @author George van den Driessche
 */
@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible
public enum SetFeature implements Feature<Set> {
  GENERAL_PURPOSE(CollectionFeature.GENERAL_PURPOSE);

  private final Set<Feature<? super Set>> implied;

import java.util.Set;

/**
 * Optional features of classes derived from {@code Multimap}.
 *
 * @author Louis Wasserman
 */
@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible
public enum MultimapFeature implements Feature<Multimap> {
  VALUE_COLLECTIONS_SUPPORT_ITERATOR_REMOVE;

  private final Set<Feature<? super Multimap>> implied;

import java.util.List;
import java.util.Set;

/**
 * Optional features of classes derived from {@code List}.
 *
 * @author George van den Driessche
 */
@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible
public enum ListFeature implements Feature<List> {
  SUPPORTS_SET,
  SUPPORTS_ADD_WITH_INDEX(CollectionFeature.SUPPORTS_ADD),
  SUPPORTS_REMOVE_WITH_INDEX(CollectionFeature.SUPPORTS_REMOVE),

import java.util.Set;

/**
 * Optional features of classes derived from {@code Set}.
 *
 * @author George van den Driessche
 */
@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible
public enum SetFeature implements Feature<Set> {
  GENERAL_PURPOSE(CollectionFeature.GENERAL_PURPOSE);

  private final Set<Feature<? super Set>> implied;

import java.util.Collections;
import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * A base implementation of {@link NetworkConnections} for undirected networks.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <E> Edge parameter type
 */
abstract class AbstractUndirectedNetworkConnections<N, E> implements NetworkConnections<N, E> {

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * An implementation of {@link NetworkConnections} for undirected networks with parallel edges.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <E> Edge parameter type
 */
final class UndirectedMultiNetworkConnections<N, E>

import java.util.Set;

/**
 * Optional features of classes derived from {@code Multimap}.
 *
 * @author Louis Wasserman
 */
@SuppressWarnings("rawtypes") // maybe avoidable if we rework the whole package?
@GwtCompatible
public enum MultimapFeature implements Feature<Multimap> {
  VALUE_COLLECTIONS_SUPPORT_ITERATOR_REMOVE;

  private final Set<Feature<? super Multimap>> implied;

import java.util.AbstractSet;
import java.util.Collections;
import java.util.Map;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * A base implementation of {@link NetworkConnections} for directed networks.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <E> Edge parameter type
 */
abstract class AbstractDirectedNetworkConnections<N, E> implements NetworkConnections<N, E> {