Subset of state, containing the elements which must match for two or more obligation transactions to be candidates for netting (this does not include the checks to enforce that everyone's amounts received are the same at the end, which is handled under the verify() function). In comparison to BilateralNetState, this doesn't include the parties' keys, as ensuring balances match on input and output is handled elsewhere. Used in cases where all parties (or their proxies) are signing, such as central clearing.