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: 20170629200720_remove_identifier_tables.rb
    path of file: ./repos/classroom/db/migrate
    
    the code of the file until where you have to start completion: class RemoveIdentifierTables < ActiveRecord::Migration[5.1]
  def change

    
  def change
    remove_column :assignments, :student_identifier_type_id
    remove_column :group_assignments, :student_identifier_type_id

    drop_table :student_identifier_types
    drop_table :student_identifiers
  end