}
  }

  private <T extends @Nullable Object> void actsLikeIteratorHelper(List<T> list) {
    // Check with modifiable copies of the list
    new PeekingIteratorTester<T>(list).test();

    // Check with unmodifiable lists
    new IteratorTester<T>(
        list.size() * 2 + 2, UNMODIFIABLE, list, IteratorTester.KnownOrder.KNOWN_ORDER) {
      @Override
      protected Iterator<T> newTargetIterator() {

import static com.google.common.collect.testing.Helpers.copyToList;
import static com.google.common.collect.testing.Helpers.getMethod;
import static com.google.common.collect.testing.IteratorFeature.MODIFIABLE;
import static com.google.common.collect.testing.IteratorFeature.UNMODIFIABLE;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_REMOVE;
import static com.google.common.collect.testing.features.ListFeature.SUPPORTS_ADD_WITH_INDEX;

 *     Collections.unmodifiableList(
 *         Arrays.asList("a", "b", "c", "d", "e"));
 * IteratorTester<String> iteratorTester =
 *     new IteratorTester<String>(
 *         6,
 *         IteratorFeature.UNMODIFIABLE,
 *         expectedElements,
 *         IteratorTester.KnownOrder.KNOWN_ORDER) {
 *       @Override
 *       protected Iterator<String> newTargetIterator() {
 *         return actualElements.iterator();
 *       }

 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;
import static com.google.common.collect.testing.IteratorFeature.UNMODIFIABLE;
import static com.google.common.truth.Truth.assertThat;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;

import org.jspecify.annotations.Nullable;

/**
 * An implementation of {@code Iterable} which throws an exception on all invocations of the {@link
 * #iterator()} method after the first, and whose iterator is always unmodifiable.
 *
 * <p>The {@code Iterable} specification does not make it absolutely clear what should happen on a
 * second invocation, so implementors have made various choices, including:
 *
 * <ul>

import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;
import static com.google.common.collect.testing.IteratorFeature.MODIFIABLE;
import static com.google.common.collect.testing.IteratorFeature.UNMODIFIABLE;
import static com.google.common.truth.Truth.assertThat;
import static java.util.Arrays.asList;
import static java.util.Collections.emptyList;

      }
    };
  }

  /** Returns the children of the specified node. Must not contain null. */
  public abstract Iterable<T> children(T root);

  /**
   * Returns an unmodifiable iterable over the nodes in a tree structure, using pre-order traversal.
   * That is, each node's subtrees are traversed after the node itself is returned.
   *

  @Synchronized
  fun queuedCalls(): List<Call> = readyAsyncCalls.map { it.call }.unmodifiable()

  /** Returns a snapshot of the calls currently being executed. */
  @Synchronized
  fun runningCalls(): List<Call> = (runningSyncCalls + runningAsyncCalls.map { it.call }).unmodifiable()

  @Synchronized
  fun queuedCallsCount(): Int = readyAsyncCalls.size

  @Synchronized

  }

  /**
   * Returns an unmodifiable view of the specified collection, preserving the interface for
   * instances of {@code SortedSet}, {@code Set}, {@code List} and {@code Collection}, in that order
   * of preference.
   *
   * @param collection the collection for which to return an unmodifiable view
   * @return an unmodifiable view of the collection
   */

  }

  /**
   * Returns an unmodifiable view of the specified collection, preserving the interface for
   * instances of {@code SortedSet}, {@code Set}, {@code List} and {@code Collection}, in that order
   * of preference.
   *
   * @param collection the collection for which to return an unmodifiable view
   * @return an unmodifiable view of the collection
   */