class ActiveModel::LazyAttributeHash

def assign_default_value(name)
  type = additional_types.fetch(name, types[name])
  value_present = true
  value = values.fetch(name) { value_present = false }
  if value_present
    delegate_hash[name] = Attribute.from_database(name, value, type)
  elsif types.key?(name)
    attr = default_attributes[name]
    if attr
      delegate_hash[name] = attr.dup
    else
      delegate_hash[name] = Attribute.uninitialized(name, type)
    end
  end
end