class Grape::Validations::Validators::ExactlyOneOfValidator

def validate_params!(params)
  keys = keys_in_common(params)
  return if keys.length == 1
  raise Grape::Exceptions::Validation.new(params: all_keys, message: message(:exactly_one)) if keys.empty?
  raise Grape::Exceptions::Validation.new(params: keys, message: message(:mutual_exclusion))
end