class Faker::IDNumber

def spanish_foreign_citizen_number
  code = 'XYZ'
  digits = Faker::Number.number(digits: 7)
  prefix = code[rand(code.length)]
  prefix_val = 'XYZ'.index(prefix).to_s
  mod = "#{prefix_val}#{digits}".to_i % 23
  check = CHECKS[mod]
  "#{prefix}-#{digits}-#{check}"
end