function defaultFormatter(key, value) {
  // Remove line breaks, tabs, spaces, .
  const validKey = replaceInvalid(key)
  // snake_case values
  const formattedKey = snakeCase(validKey)
  // special case for firstName & lastName
  if (formattedKey === 'first_name' || formattedKey === 'last_name') {
    return [ formattedKey.replace(/_/, ''), value ]
  }
  return [ formattedKey, value ]
}
Identify a visitor in hubspot
@link https://developers.hubspot.com/docs/methods/tracking_code_api/identify_visitor
@example

analytics.identify({
  name: 'bob',
  email: 'bob@bob.com' // email is required
})