refactor-users.js

const TwitterUser = Interface('TwitterUser')({
  twitterId: type('string'),
  twitterUsername: type('string')
},{
  trim: true,
  extends: User,
  rename: { twitter_id: 'twitterId', twitter_username: 'twitterUsername' }
})

const getUser = () => async dispatch => {
  dispatch(fetchUsersBegin())

  try {
    const response = await twitterService.getUser()
    const ValidTwitterUser = implement(TwitterUser)(response)
    dispatch(fetchUserSuccess(ValidTwitterUser))
  } catch (err) {
    dispatch(fetchUserError(err))
  }
}