You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: validate_os_family.rb
    path of file: ./repos/foreman/app/models/concerns
    
    the code of the file until where you have to start completion: module ValidateOsFamily
  extend ActiveSupport::Concern

  module ClassMethods
    def validate_inclusion_in_families(family_attr_name)
      validates family_attr_name,
        :inclusion => {
          :in => Operatingsystem.families,
          
    
    def validate_inclusion_in_families(family_attr_name)
      validates family_attr_name,
        :inclusion => {
          :in => Operatingsystem.families,
          :message => N_("must be one of [ %s ]" % Operatingsystem.families.join(", ")),
        },
        :allow_nil => true

      define_method "#{family_attr_name}=" do |value|
        self[family_attr_name] = value.presence
      end
    end