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: asset_link.rb
    path of file: ./repos/sequencescape/app/models
    
    the code of the file until where you have to start completion: # frozen_string_literal: true
# AssetLink is powered by acts-as-dag
# @see https://github.com/resgraph/acts-as-dag
#
# Briefly, acts-as-dag attempts to implement a directed-acy
    
  def destroy!; end

  module Associations
    def self.included(base)
      base.class_eval do
        extend ClassMethods

        has_dag_links link_class_name: 'AssetLink'
        has_many :child_plates, through: :links_as_parent, source: :descendant, class_name: 'Plate'
        has_many :child_tubes, through: :links_as_parent, source: :descendant, class_name: 'Tube'
        has_many :parent_tubes, through: :links_as_child, source: :ancestor, class_name: 'Tube'
        has_many :parent_plates, through: :links_as_child, source: :ancestor, class_name: 'Plate'
      end
      base.extend(ClassMethods)
    end

    module ClassMethods
      def has_one_as_child(name, scope) # rubocop:todo Metrics/MethodLength
        plural_name = name.to_s.pluralize.to_sym
        has_many(plural_name, scope, through: :links_as_child, source: :ancestor)
        line = __LINE__ + 1
        class_eval(
          "
          def #{name}
            #{plural_name}.first
          end

          def #{name}=(value)
            raise RuntimeError, 'Value for #{name} must be saved' if value.new_record?
            old_value = self.#{name}
            parents.destroy(old_value) if old_value.present?
            AssetLink.create_edge!(value, self)
          end

          def has_#{name}?
            #{name}.present?
          end
        ",
          __FILE__,
          line
        )
      end
    end