docs: public BranchingFactorGraph buildConnectedComponent(VariableNumMap vars) {
      // Not implemented for branching graphs.
      Preconditions.checkState(isRoot && children.size() == 0);
  
      FactorGraph componentFactorGraph = FactorGraph.getConnectedComponent(vars, variableFactorMap,
          factorVariableMap, variables, factors, factorNames, VariableNumMap.EMPTY, Assignment.EMPTY, null);
  
      return new BranchingFactorGraph(componentFactorGraph.conditional(assignment), Lists.<ChildBfg>newArrayList());
    }