How to use the rebass.Heading function in rebass

import * as Rebass from 'rebass'
import { Link } from 'react-router-dom'
import { Consumer as Refunk } from 'refunk'

const components = Object.assign({}, Rebass, {
  Link,
  Refunk,
  h2: Rebass.Heading,
  h3: Rebass.Heading
})

const theme = Rebass.theme

export default {
  ...components,
  theme
}

import * as Rebass from 'rebass'
import { Link } from 'react-router-dom'
import { Consumer as Refunk } from 'refunk'

const components = Object.assign({}, Rebass, {
  Link,
  Refunk,
  h2: Rebass.Heading,
  h3: Rebass.Heading
})

const theme = Rebass.theme

export default {
  ...components,
  theme
}

export const Checkbox = R.Checkbox
export const Circle = R.Circle
export const Close = R.Close
export const Code = R.Code
export const Column = R.Column
export const Container = R.Container
export const DarkMode = R.DarkMode
export const Divider = R.Divider
export const Donut = R.Donut
export const Dot = R.Dot
export const Drawer = R.Drawer
export const Embed = R.Embed
export const Fixed = R.Fixed
export const Flex = R.Flex
export const Group = R.Group
export const Heading = R.Heading
export const Image = R.Image
export const Input = R.Input
export const Label = R.Label
export const Lead = R.Lead
export const Link = R.Link
export const Measure = R.Measure
export const Message = R.Message
export const Modal = R.Modal
export const NavLink = R.NavLink
export const Overlay = R.Overlay
export const Panel = R.Panel
export const Position = R.Position
export const Pre = R.Pre
export const Progress = R.Progress
export const Provider = R.Provider
export const Radio = R.Radio