How to use the @ephox/boulder.FieldSchema.defaultedFunction function in @ephox/boulder

const launchButtonSchema = ValueSchema.objOf(baseToolbarButtonFields.concat([
  FieldSchema.defaulted('type', 'contextformbutton')
]));

const launchToggleButtonSchema = ValueSchema.objOf(baseToolbarToggleButtonFields.concat([
  FieldSchema.defaulted('type', 'contextformtogglebutton')
]));

const toggleOrNormal = ValueSchema.choose('type', {
  contextformbutton: contextButtonSchema,
  contextformtogglebutton: contextToggleButtonSchema
});

const contextFormSchema = ValueSchema.objOf([
  FieldSchema.defaulted('type', 'contextform'),
  FieldSchema.defaultedFunction('initValue', () => ''),
  FieldSchema.optionString('label'),
  FieldSchema.strictArrayOf('commands', toggleOrNormal),
  FieldSchema.optionOf('launch', ValueSchema.choose('type', {
    contextformbutton: launchButtonSchema,
    contextformtogglebutton: launchToggleButtonSchema
  }))
].concat(contextBarFields));

const contextToolbarSchema = ValueSchema.objOf([
  FieldSchema.defaulted('type', 'contexttoolbar'),
  FieldSchema.strictString('items')
].concat(contextBarFields));

export const createContextToolbar = (spec: ContextToolbarApi): Result> => {
  return ValueSchema.asRaw('ContextToolbar', contextToolbarSchema, spec);
};

storage: Cell;
}

export interface BaseDialogMenuButtonInstanceApi {
  isDisabled: () => boolean;
  setDisabled: (state: boolean) => void;
  isActive: () => boolean;
  setActive: (state: boolean) => void;
}

export const baseDialogMenuButtonFields = [
  FieldSchema.optionString('text'),
  FieldSchema.optionString('tooltip'),
  FieldSchema.optionString('icon'),
  FieldSchema.strictArrayOf('items', dialogToggleMenuItemSchema),
  FieldSchema.defaultedFunction('onSetup', () => Fun.noop),
  FieldSchema.defaulted('storage', Cell(false))
];

initValue?: () => string;
  label?: string;
  launch?: ContextFormLaunchButtonApi | ContextFormLaunchToggleButtonApi;
  commands: Array;
}

export interface ContextForm extends ContextBar {
  type: 'contextform';
  initValue: () => string;
  label: Option;
  launch: Option;
  commands: Array;
}

const contextBarFields = [
  FieldSchema.defaultedFunction('predicate', () => false),
  FieldSchema.defaultedStringEnum('scope', 'node', ['node', 'editor']),
  FieldSchema.defaultedStringEnum('position', 'selection', ['node', 'selection', 'line']),
];

const contextButtonSchema = ValueSchema.objOf(baseToolbarButtonFields.concat([
  FieldSchema.defaulted('type', 'contextformbutton'),
  FieldSchema.defaulted('primary', false),
  FieldSchema.strictFunction('onAction'),
  FieldSchema.state('original', Fun.identity)
]));

const contextToggleButtonSchema = ValueSchema.objOf(baseToolbarToggleButtonFields.concat([
  FieldSchema.defaulted('type', 'contextformbutton'),
  FieldSchema.defaulted('primary', false),
  FieldSchema.strictFunction('onAction'),
  FieldSchema.state('original', Fun.identity)

...baseButtonFields,
  FieldSchema.strictString('text')
];

const normalButtonFields = [
  FieldSchema.strictStringEnum('type', ['submit', 'cancel', 'custom']),
  ...dialogButtonFields
];

const menuButtonFields = [
  FieldSchema.strictStringEnum('type', ['menu']),
  FieldSchema.optionString('text'),
  FieldSchema.optionString('tooltip'),
  FieldSchema.optionString('icon'),
  FieldSchema.strictArrayOf('items', dialogToggleMenuItemSchema),
  FieldSchema.defaultedFunction('onSetup', () => Fun.noop),
  ...baseButtonFields
];

export const dialogButtonSchema = ValueSchema.choose(
  'type',
  {
    submit: normalButtonFields,
    cancel: normalButtonFields,
    custom: normalButtonFields,
    menu: menuButtonFields
  }
);