S4-class for a list of internal fluxes with indexed by (source and destination pool) names
InternalFluxList_by_PoolName
as.numeric,InternalFluxList_by_PoolName-method
by_PoolIndex,InternalFluxList_by_PoolName,character,character-method
UnBoundNonLinDecompOp_by_PoolNames,InternalFluxList_by_PoolName,OutFluxList_by_PoolName,character-method