Rails How to define a macro to use only within factories.rb - factory-bot

Question

I'm using FactoryGirl in a Rails application for RSpec functional testing. While writing factories I came across a need for defining private method or macro to remove the duplicate code in factories. The macros should be such that it can only be called from factories definition. Kindly help
factory :subscriber, :class => Subscriber do
sequence(:name) { |n| "test_user_#{n}" }
sequence(:email) { |n| "test_user_#{n}#example.com"}
association :authentication, factory: :authentication
factory :subscriber_with_subscription do
ignore do
payment_pending_subscriptions 0
purchased_subscriptions 0
active_subscriptions 0
end
after(:create) do |subscriber, evaluator|
count = evaluator.payment_pending_subscriptions
FactoryGirl.create_list(:subscription, count, status: 'payment_pending', :subscriber => subscriber) if count >0
count = evaluator.purchased_subscriptions
FactoryGirl.create_list(:subscription, count, status: 'purchased', :subscriber => subscriber) if count > 0
count = evaluator.active_subscriptions
FactoryGirl.create_list(:subscription, count, status: 'active', :subscriber => subscriber) if count > 0
end
end
end
if I can define a method inside the factory such that
def create_subs count, status
FactoryGirl.create_list(:subscription, count, status: status, :subscriber => subscriber) if count > 0
end
Then the calls can be reduced to one line / state
create_subs evaluate.purchased_subscription, "purchased_subscription"
But even after defining create_subs, it gives error that it is not found.