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: 20160524234655_create_student_identifiers.rb
    path of file: ./repos/classroom/db/migrate
    
    the code of the file until where you have to start completion: class CreateStudentIdentifiers < ActiveRecord::Migration[4.2]
  def change
    create_table :student_identifier_types do |t|
      t.belongs_to :organization, index: true
      t.string :name,          null: false
      t.string :descript
    
  def change
    create_table :student_identifier_types do |t|
      t.belongs_to :organization, index: true
      t.string :name,          null: false
      t.string :description,   null: false
      t.integer :content_type, null: false
      t.datetime :created_at,  null: false
      t.datetime :updated_at,  null: false
      t.datetime :deleted_at
    end

    create_table :student_identifiers do |t|
      t.belongs_to :organization, index: true
      t.belongs_to :user,         index: true
      t.belongs_to :student_identifier_type
      t.string :value,        null: false
      t.datetime :created_at, null: false
      t.datetime :updated_at, null: false
      t.datetime :deleted_at
    end

    add_column :assignments, :student_identifier_type_id, :integer
    add_column :group_assignments, :student_identifier_type_id, :integer

    add_index :student_identifiers, :student_identifier_type_id
  end