def attributes
      {
        :vault_id => vault_id,
        :currency => currency,
        :card_number => card_number,
        :cvv_number => cvv_number,
        :expires_on => expires_on,
        :first_name => first_name,
        :last_name => last_name,
        :street_address => street_address,
        :locality => locality,
        :region => region,
        :postal_code => postal_code,
        :country => country,
        :phone => phone
      }
    end
def attributes
      {
        :vault_id => vault_id,
        :currency => currency,
        :card_number => card_number,
        :cvv_number => cvv_number,
        :expires_on => expires_on,
        :first_name => first_name,
        :last_name => last_name,
        :street_address => street_address,
        :locality => locality,
        :region => region,
        :postal_code => postal_code,
        :country => country,
        :phone => phone
      }
    end
The unique, gateway-generated identifier for this credit card.

 You may define any of the CreditCard attributes by passing a hash
 with the attribute name as the key:

     CreditCard.new(:card_number => '4111....')