* be output to the latest value referenced by System.out/err variables. By setting this parameter to true,
     * the output stream will be cached, i.e. assigned once at initialization time and re-used independently of
     * the current value referenced by System.out/err.
     *
     * @since 4.0.0
     */

   * (used as the reference iterator) against a {@code PeekingIterator} that *wraps* such an
   * iterator (used as the target iterator).
   *
   * <p>This IteratorTester makes copies of the master so that it can later verify that {@link
   * PeekingIterator#remove()} removes the same elements as the reference's iterator {@code
   * remove()}.
   */

 * <li>{@code classDocbookDir} - A directory that should contain docbook template for each class referenced in main docbook template.</li>
 * </ul>
 *
 * Produces the following:
 * <ul>
 * <li>A docbook book XML file containing the reference.</li>
 * <li>A meta-data file containing information about where the canonical documentation for each class can be found:

   * (used as the reference iterator) against a {@code PeekingIterator} that *wraps* such an
   * iterator (used as the target iterator).
   *
   * <p>This IteratorTester makes copies of the master so that it can later verify that {@link
   * PeekingIterator#remove()} removes the same elements as the reference's iterator {@code
   * remove()}.
   */

      }
    }
  }

  /** A weakly referenced value that also has a reference to its containing entry. */
  interface WeakValueReference<K, V, E extends InternalEntry<K, V, E>> {
    /**
     * Returns the current value being referenced, or {@code null} if there is none (e.g. because

      const auto& iter = input_nodes.find(node);
      if (iter == input_nodes.end()) {
        // This node is not referenced in inputs. Add it to the body.
        body_nodes->push_back(node);
      } else {
        // This node is referenced in inputs. Currently, we place an
        // artificial restriction and require that when num_opers=-1, such
        // nodes must have a single output.

      }
    }
  }

  /** A weakly referenced value that also has a reference to its containing entry. */
  interface WeakValueReference<K, V, E extends InternalEntry<K, V, E>> {
    /**
     * Returns the current value being referenced, or {@code null} if there is none (e.g. because

    # Build a set of directory-based package roots (e.g. docs_src/bigger_applications/app_py39)
    # where at least one file is referenced in docs. All files in these directories
    # should be kept since they may be internally imported by the referenced files.
    used_package_dirs: set[Path] = set()
    for py_file in docs_src_path.rglob("*.py"):
        if py_file.name == "__init__.py":
            continue

                    "schema": {
                        "$ref": "#/components/schemas/HTTPValidationError"
                    }
                }
            }
        }
    }
}
```

The schemas are referenced to another place inside the OpenAPI schema:

```JSON hl_lines="4-16"
{
    "components": {
        "schemas": {
            "Message": {
                "title": "Message",
                "required": [

/** Implementation of an {@link Optional} containing a reference. */
@GwtCompatible
final class Present<T> extends Optional<T> {
  private final T reference;

  Present(T reference) {
    this.reference = reference;
  }

  @Override
  public boolean isPresent() {
    return true;
  }

  @Override
  public T get() {
    return reference;
  }

  @Override
  public T or(T defaultValue) {