def transaction_group(transaction)
      { requested_date: transaction.requested_date,
        batch_booking:  transaction.batch_booking,
        service_level:  transaction.service_level,
        category_purpose: transaction.category_purpose
      }
    end
def transaction_group(transaction)
      { requested_date: transaction.requested_date,
        batch_booking:  transaction.batch_booking,
        service_level:  transaction.service_level,
        category_purpose: transaction.category_purpose
      }
    end
Find groups of transactions which share the same values of some attributes