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: seeds.rb
    path of file: ./repos/activity_notification/spec/rails_app/db
    
    the code of the file until where you have to start completion: # coding: utf-8
# T
    
def clean_database
  models = [Comment, Article, Admin, User]
  if ENV['AN_USE_EXISTING_DYNAMODB_TABLE']
    ActivityNotification::Notification.where('id.not_null': true).delete_all
    ActivityNotification::Subscription.where('id.not_null': true).delete_all
  else
    models.concat([ActivityNotification::Notification, ActivityNotification::Subscription])
  end