code: public static MultiColumnRelation createSingleMarkerInRelation(List<ColumnIdentifier.Raw> entities, Tuples.INRaw inMarker)
      {
          return new MultiColumnRelation(entities, Operator.IN, null, null, inMarker);
      }
docs: Creates a multi-column IN relation with a marker for the IN values.
  For example: "SELECT ... WHERE (a, b) IN ?"
  @param entities the columns on the LHS of the relation
  @param inMarker a single IN marker