Map<R, V> output = new LinkedHashMap<>();
    Iterator<Entry<R, Map<C, V>>> iterator = backingMap.entrySet().iterator();
    while (iterator.hasNext()) {
      Entry<R, Map<C, V>> entry = iterator.next();
      V value = entry.getValue().remove(column);
      if (value != null) {
        output.put(entry.getKey(), value);
        if (entry.getValue().isEmpty()) {
          iterator.remove();
        }
      }
    }

  }

  @CollectionSize.Require(ONE)
  @CollectionFeature.Require(SUPPORTS_ITERATOR_REMOVE)
  public void testKeysEntrySetIteratorRemove() {
    Multiset<K> keys = multimap().keys();
    Iterator<Multiset.Entry<K>> itr = keys.entrySet().iterator();
    assertEquals(Multisets.immutableEntry(k0(), 1), itr.next());
    itr.remove();
    assertTrue(multimap().isEmpty());
  }

  @CollectionSize.Require(SEVERAL)

  public void testCopyOf_iterator_oneElementRepeated() {
    Iterator<String> iterator = Iterators.forArray("a", "a", "a");
    Set<String> set = copyOf(iterator);
    assertEquals(singleton("a"), set);
  }

  public void testCopyOf_iterator_general() {
    Iterator<String> iterator = Iterators.forArray("a", "b", "a");
    Set<String> set = copyOf(iterator);
    assertEquals(2, set.size());
    assertTrue(set.contains("a"));

    Iterator<T> iteratorA = iterableA.iterator();
    Iterator<T> iteratorB = iterableB.iterator();

    while (iteratorA.hasNext() && iteratorB.hasNext()) {
      if (!elementEquivalence.equivalent(iteratorA.next(), iteratorB.next())) {
        return false;
      }
    }

    return !iteratorA.hasNext() && !iteratorB.hasNext();
  }

  @Override

    assertNextThrows(iterator);

    /* Checks the case where a later element throws an exception. */

    list = Lists.newArrayList(1, 2);
    iterator = peekingIterator(new ThrowsAtEndIterator<Integer>(list));
    assertTrue(iterator.hasNext());
    iterator.next();
    assertTrue(iterator.hasNext());
    iterator.next();
    assertNextThrows(iterator);
  }

  private void assertNextThrows(Iterator<?> iterator) {

        @Override
        public @Nullable Object execute(Iterator<?> iterator) {
          iterator.remove();
          return null;
        }
      };

  private static final IteratorOperation NEXT_METHOD =
      new IteratorOperation() {
        @Override
        public @Nullable Object execute(Iterator<?> iterator) {
          return iterator.next();
        }
      };

     */
    public boolean isChildOfRootNode() {
        return parent != null && parent.parent == null;
    }

    public Iterator<ResolutionNode> getChildrenIterator() {
        return children.iterator();
    }

    public int getDepth() {
        return depth;
    }

    public List<ArtifactRepository> getRemoteRepositories() {
        return remoteRepositories;

    Iterator<String> iterator = skip(list, 2).iterator();
    assertThrows(IllegalStateException.class, () -> iterator.remove());
  }

  public void testSkip_allOfImmutableList_modifiable() {
    List<String> list = ImmutableList.of("a", "b");
    Iterator<String> iterator = skip(list, 2).iterator();
    assertThrows(UnsupportedOperationException.class, () -> iterator.remove());
  }

        TestIterator iterator = new TestIterator(null);

        // Verify iteration
        assertTrue(iterator.hasNext());
        assertSame(resource, iterator.next());

        assertTrue(iterator.hasNext());
        assertSame(resource, iterator.next());

        assertTrue(iterator.hasNext());
        assertSame(resource, iterator.next());

        assertFalse(iterator.hasNext());

            } catch (MultipleArtifactsNotFoundException e) {

                Collection<Artifact> missing = new HashSet<>(e.getMissingArtifacts());

                for (Iterator<Artifact> it = missing.iterator(); it.hasNext(); ) {
                    String key = ArtifactUtils.key(it.next());
                    if (projectIds.contains(key)) {
                        it.remove();
                    }