}
    }
  }

  /** 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

     * 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
     */

                    "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": [

// inspect values. This would let people e.g. copy over most attributes and then
// modify some based on their values.

// A reference to an op's name -> attribute mapping
typedef struct TFE_OpAttrs TFE_OpAttrs;

// Fetch a reference to `op`'s attributes. The returned reference is only valid
// while `op` is alive.
TF_CAPI_EXPORT extern const TFE_OpAttrs* TFE_OpGetAttrs(const TFE_Op* op);

/** 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) {

    if (reference == null) {
      throw new NullPointerException();
    }
    return reference;
  }

  /**
   * Ensures that an object reference passed as a parameter to the calling method is not null.
   *
   * @param reference an object reference
   * @param errorMessage the exception message to use if the check fails; will be converted to a

/** 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) {

    if (reference == null) {
      throw new NullPointerException();
    }
    return reference;
  }

  /**
   * Ensures that an object reference passed as a parameter to the calling method is not null.
   *
   * @param reference an object reference
   * @param errorMessage the exception message to use if the check fails; will be converted to a

                            reference = "AetherClassNotFound";
                        }
                    }
                }

                if (reference == null || reference.isEmpty()) {
                    reference = getReference(dejaVu, cause);
                }

                if (reference == null || reference.isEmpty()) {
                    reference = exception.getClass().getSimpleName();