superset/superset-frontend/packages/superset-ui-demo/.storybook/themeDecorator.js

// themeDecorator.js
import React from 'react';
import { supersetTheme, ThemeProvider } from '@superset-ui/core';

const ThemeDecorator = storyFn => (
  <ThemeProvider theme={supersetTheme}>{storyFn()}</ThemeProvider>
);

export default ThemeDecorator;