docs: public static ImmutableMultimap<Symbol, Symbol> loadSymbolMultimap(CharSource multimapSource)
        throws IOException {
      final ImmutableMultimap<String, String> stringMM = loadStringMultimap(multimapSource);
      final ImmutableMultimap.Builder<Symbol, Symbol> ret = ImmutableMultimap.builder();
  
      for (final Map.Entry<String, Collection<String>> entry : stringMM.asMap().entrySet()) {
        ret.putAll(Symbol.from(entry.getKey()),
            Collections2.transform(entry.getValue(), Symbol.FromString));
      }
  
      return ret.build();
    }