The file in TypeORM Migration must contain a TypeScript or JavaScript code that defines the migration operations to be performed on the database schema.
The file must also export a class that extends the TypeORM Migration class, and specifies the up and down methods for migrating the database schema up and down, respectively.
Additionally, the file may define a DataSource instance that connects to the database, but this is not required. If a DataSource is defined, it must be exported along with the migration class.
