class ActiveRecord::ConnectionAdapters::SavepointTransaction

def initialize(connection, savepoint_name, parent_transaction, **options)
  super(connection, **options)
  parent_transaction.state.add_child(@state)
  if isolation_level
    raise ActiveRecord::TransactionIsolationError, "cannot set transaction isolation in a nested transaction"
  end
  @savepoint_name = savepoint_name
end