code: def setup(self):
      
      cmds = [
        """
          create table if not exists relations (
            id integer not null primary key,
            name text not null unique,
            completed_at datetime
          );
        """,
        """
          create table if not exists transfers (
            relation_id integer not null references relations (id) on delete cascade,
            old_id text not null,
            new_id text,
            primary key (relation_id, old_id)
          );
        """,
        """
          create index if not exists transfers_relation_id_idx on transfers (relation_id);
        """
      ]
  
      for cmd in cmds:
        self.data_access.execute(cmd)
      self.data_access.commit()
      return self
docs: Creates the default relations and transfers tables. The SQL used may not work on all
      databases. (It was written for SQLite3)