Instruments

LMECashForward	Spot LME Forward, traded on the start_date.
LMEForward	Generic LME Forward with arbitrary delivery date (that can be more than 3 months away, and doesn't have to be 3rd Wednesday.
LME3MForward	Outright 3 Month LME Forward, traded on the start_date.
LMEFuture	Synthetic 3rd Wednesday future (or rather forward), priced off outright 3M forward and spread contract.
LMESpreadContract	Spread contract simultaneously buying 3 Month forward (LME3MForward) and selling 3rd Wednesday forward (LMEFuture).
CommodityRollingForward	A class representing a commodity forward.