I have a certain requirement for backtesting. I want to backtest my algorithm against the closest expiry for calls and puts. How can I achieve this? For example: I want to use 20th May expiry while backtesting data from 14th to 20th and 13th May expiry while back testing data before 13th. How is this possible ? The instrument id for 13th expiry is not present( as it has expired). Any possible workaround for this?