If this summary has a univariate Marginal for variable v, return it in an Option; otherwise return None.
If this Summary has a Marginal that touches all or a subset of the neighbors of this factor return the Marginal with the maximally-available subset.
If this Summary has a univariate Marginal for variable v, return it; otherwise return null.
The collection of all Marginals available in this Summary
All the variables for which this Summary has a univariate Marginal.