docs: public Optional<ConceptBuilder> tryBuilder(Variable var) {
          var = equivalentVars.componentOf(var);
  
          if (concepts.containsKey(var)) {
              return Optional.empty();
          }
  
          ConceptBuilder builder = conceptBuilders.get(var);
  
          if (builder != null) {
              return Optional.of(builder);
          }
  
          builder = ConceptBuilder.of(this, var);
          conceptBuilders.put(var, builder);
          return Optional.of(builder);
      }