```ruby
module Extensions::ActiveRecord::Base
  def self.included(class_)
    class_.class_eval do
      def self.currently_valid
        where do
          (valid_from.nil? || valid_from <= DateTime.now) &&
            (valid_to.nil? || valid_to >= DateTime.now)
        end
      end
    end
  end

  def currently_valid?
    (valid_from.nil? || valid_from <= DateTime.now) &&
      (valid_to.nil? || valid_to >= DateTime.now)
  end
end
```

Add more helper functions for bounded objects
user
```ruby
module Extensions::ActiveRecord::Base
  def self.included(class_)
    class_.class_eval do
      def self.currently_valid
        where do
          (valid_from.nil? || valid_from <= DateTime.now) &&
            (valid_to.nil? || valid_to >= DateTime.now)
        end
      end
    end
  end

  # @return [Bool] True if valid_from is a future time
  def not_yet_valid?
    !valid_from.nil? && valid_from > DateTime.now
  end

  # @return [Bool] True if current time is between valid_from and valid_to
  def currently_valid?
    (valid_from.nil? || valid_from <= DateTime.now) &&
      (valid_to.nil? || valid_to >= DateTime.now)
  end

  # @return [Bool] True if valid_to is a past time
  def expired?
    !valid_to.nil? && DateTime.now > valid_to
  end
end
```
assistant