How can / should I override the `build` method for a my model?

def my_decoder(instance, **kwargs):
    instance.decoded_stuff = decode_this(instance.encoded.stuff)

models.signals.post_init.connect(my_decoder, UserData)

class Seat(models.Model):
    page = models.ForeignKey(Car)
    position = models.IntegerField()

    class Meta:
        ordering = ('position', )

module MyAppModel
  def test
    'test'
  end
end
ActiveRecord::Base.send :include, MyAppModel

require Rails.root.join 'app/models/namespace/my_model'

static class SimpleTextHolder extends RecyclerView.ViewHolder {
    // ...
}

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true

  def self.column_names_without(*names)
    column_names - (%w[created_at updated_at] | names)
  end
end

ActiveAdmin.register Question do
  index do
    selectable_column
    Question.column_names_without('quiz_id').each do |c|
      column c.to_sym
    end
  end

  show do
    attributes_table do
      Question.column_names_without('quiz_id').each do |c|
        row c.to_sym
      end
    end
  end

end