```ruby
# frozen_string_literal: true
module Panther
  module Representer
    module Timestamped
      def self.included(klass)
        klass.class_eval <<-RUBY
          property :created_at, exec_context: :decorator, if: -> (_) { respond_to?(:created_at) }
          property :updated_at, exec_context: :decorator, if: -> (_) { respond_to?(:updated_at) }

          def created_at
            represented.created_at.to_i
          end

          def updated_at
            represented.updated_at.to_i
          end
        RUBY
      end
    end
  end
end
```

Use class_eval with block in Representer::Timestamped
user
```ruby
# frozen_string_literal: true
module Panther
  module Representer
    module Timestamped
      def self.included(klass)
        klass.class_eval do
          property :created_at, exec_context: :decorator, if: -> (_) { respond_to?(:created_at) }
          property :updated_at, exec_context: :decorator, if: -> (_) { respond_to?(:updated_at) }
        end
      end

      def created_at
        represented.created_at.to_i
      end

      def updated_at
        represented.updated_at.to_i
      end
    end
  end
end
```
assistant