import java.util.Map;
import java.util.Set;
import javax.annotation.CheckForNull;

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

import com.google.common.collect.ImmutableBiMap;
import java.util.Collections;
import java.util.Map;
import java.util.Set;

/**
 * An implementation of {@link NetworkConnections} for undirected networks.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <E> Edge parameter type
 */
@ElementTypesAreNonnullByDefault
final class UndirectedNetworkConnections<N, E> extends AbstractUndirectedNetworkConnections<N, E> {

import java.util.Set;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A class to facilitate the set returned by {@link Graph#edges()}.
 *
 * @author James Sexton
 */
@ElementTypesAreNonnullByDefault
abstract class EndpointPairIterator<N> extends AbstractIterator<EndpointPair<N>> {
  private final BaseGraph<N> graph;
  private final Iterator<N> nodeIterator;

      <email></email>
      <organization></organization>
      <roles>
        <role>Developer</role>
      </roles>
    </developer>
    <developer>
      <id>jtaylor</id>
      <name>James Taylor</name>
      <email>james@jamestaylor.org</email>
      <organization></organization>
      <roles>
        <role>Developer</role>
      </roles>
    </developer>
    <developer>
      <id>dandiep</id>

 *
 * <p>The {@link #outEdgeToNode} map allows this class to work on networks with parallel edges. See
 * {@link EdgesConnecting} for a class that is more efficient but forbids parallel edges.
 *
 * @author James Sexton
 * @param <E> Edge parameter type
 */
@ElementTypesAreNonnullByDefault
abstract class MultiEdgesConnecting<E> extends AbstractSet<E> {

  private final Map<E, ?> outEdgeToNode;
  private final Object targetNode;

import com.google.common.collect.ImmutableBiMap;
import java.util.Collections;
import java.util.Map;
import java.util.Set;

/**
 * An implementation of {@link NetworkConnections} for directed networks.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <E> Edge parameter type
 */
@ElementTypesAreNonnullByDefault
final class DirectedNetworkConnections<N, E> extends AbstractDirectedNetworkConnections<N, E> {

      <email></email>
      <organization></organization>
      <roles>
        <role>Developer</role>
      </roles>
    </developer>
    <developer>
      <id>jtaylor</id>
      <name>James Taylor</name>
      <email>james@jamestaylor.org</email>
      <organization></organization>
      <roles>
        <role>Developer</role>
      </roles>
    </developer>
    <developer>
      <id>dandiep</id>

      <email></email>
      <organization></organization>
      <roles>
        <role>Developer</role>
      </roles>
    </developer>
    <developer>
      <id>jtaylor</id>
      <name>James Taylor</name>
      <email>james@jamestaylor.org</email>
      <organization></organization>
      <roles>
        <role>Developer</role>
      </roles>
    </developer>
    <developer>
      <id>dandiep</id>

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import javax.annotation.CheckForNull;

/**
 * An implementation of {@link GraphConnections} for undirected graphs.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 * @param <V> Value parameter type
 */
@ElementTypesAreNonnullByDefault
final class UndirectedGraphConnections<N, V> implements GraphConnections<N, V> {

      <email />
      <organization />
      <roles>
        <role>Developer</role>
      </roles>
    </developer>
    <developer>
      <id>jtaylor</id>
      <name>James Taylor</name>
      <email>james@jamestaylor.org</email>
      <organization />
      <roles>
        <role>Developer</role>
      </roles>
    </developer>
    <developer>
      <id>dandiep</id>