docs: private static Map<Symbol, Aggregation> inputsAsOutputs(Map<Symbol, Aggregation> assignments)
      {
          ImmutableMap.Builder<Symbol, Aggregation> builder = ImmutableMap.builder();
          for (Map.Entry<Symbol, Aggregation> entry : assignments.entrySet()) {
              // Should only have one input symbol
              Symbol input = getOnlyElement(SymbolsExtractor.extractAll(entry.getValue().getCall()));
              builder.put(input, entry.getValue());
          }
          return builder.build();
      }