@ParametricNullness K fromKey, @ParametricNullness K toKey) {
    return subMap(fromKey, true, toKey, false);
  }

  @Override
  public NavigableMap<K, V> subMap(
      @ParametricNullness K fromKey,
      boolean fromInclusive,
      @ParametricNullness K toKey,
      boolean toInclusive) {
    return delegate().subMap(fromKey, fromInclusive, toKey, toInclusive);
  }

  @Override

    }

    @Override
    public NavigableMap<K, Collection<V>> headMap(@ParametricNullness K toKey) {
      return headMap(toKey, false);
    }

    @Override
    public NavigableMap<K, Collection<V>> headMap(@ParametricNullness K toKey, boolean inclusive) {
      return new NavigableAsMap(sortedMap().headMap(toKey, inclusive));
    }

    @Override

      @ParametricNullness K fromKey, @ParametricNullness K toKey) {
    return subMap(fromKey, true, toKey, false);
  }

  @Override
  public NavigableMap<K, V> subMap(
      @ParametricNullness K fromKey,
      boolean fromInclusive,
      @ParametricNullness K toKey,
      boolean toInclusive) {
    return delegate().subMap(fromKey, fromInclusive, toKey, toInclusive);
  }

  @Override

        Cut<C> fromKey, boolean fromInclusive, Cut<C> toKey, boolean toInclusive) {
      return subMap(
          Range.range(
              fromKey, BoundType.forBoolean(fromInclusive),
              toKey, BoundType.forBoolean(toInclusive)));
    }

    @Override
    public NavigableMap<Cut<C>, Range<C>> headMap(Cut<C> toKey, boolean inclusive) {
      return subMap(Range.upTo(toKey, BoundType.forBoolean(inclusive)));
    }

    * Send the invoice to the client.
    * Collect the money from the client.
    * Send a notification back to the API user (the external developer), as a callback.
        * At this point is that the API will somehow send a POST request to the
            external API with the notification of the invoice event
            (e.g. "payment successful").
    """
    # Send the invoice, collect the money, send the notification (the callback)

		{arg: "", wantKey: "", wantValue: ""},
	}
	for _, tt := range tests {
		t.Run(tt.arg, func(t *testing.T) {
			gotKey, gotValue := splitEqual(tt.arg)
			if gotKey != tt.wantKey {
				t.Errorf("splitEqual(%v) got = %v, want %v", tt.arg, gotKey, tt.wantKey)
			}
			if gotValue != tt.wantValue {
				t.Errorf("splitEqual(%v) got1 = %v, want %v", tt.arg, gotValue, tt.wantValue)
			}
		})
	}

      standardClear();
    }

    @Override
    public boolean isEmpty() {
      return standardIsEmpty();
    }

    @Override
    public SortedMap<K, V> subMap(K fromKey, K toKey) {
      return standardSubMap(fromKey, toKey);
    }

    @Override
    public @Nullable Entry<K, V> lowerEntry(K key) {
      return standardLowerEntry(key);
    }

    @Override
    public @Nullable K lowerKey(K key) {

 * it delegates to other components that potentially encounter problems. Then, the problem reporter can focus on
 * providing a simple error message, leaving the donkey work of creating a nice model problem to this component.
 *
 */
class DefaultModelProblemCollector implements ModelProblemCollector {

    private final ModelBuilderResult result;

   * referencing the type variables seem worthwhile.
   */
  final void checkNoDuplicate(R rowKey, C columnKey, @CheckForNull V existingValue, V newValue) {
    checkArgument(
        existingValue == null,
        "Duplicate key: (row=%s, column=%s), values: [%s, %s].",
        rowKey,
        columnKey,
        newValue,
        existingValue);
  }

    }

    @Override
    public NavigableMap<K, Collection<V>> headMap(@ParametricNullness K toKey) {
      return headMap(toKey, false);
    }

    @Override
    public NavigableMap<K, Collection<V>> headMap(@ParametricNullness K toKey, boolean inclusive) {
      return new NavigableAsMap(sortedMap().headMap(toKey, inclusive));
    }

    @Override