- address
- +keys:
    zipcode: [str, {len: 5, match: '^\d{5}$', required: Yes}]
    country: [str, {is: US}]
  -keys:
    postcode: ~
  -allowed_keys:  [postcode]
  -required_keys: [postcode]
  +required_keys: [zipcode]
  +allowed_keys:  [zipcode]
