docs: public static ImmutableMap<Symbol, Symbol> loadSymbolMap(CharSource source) throws IOException {
      final ImmutableMap.Builder<Symbol, Symbol> ret = ImmutableMap.builder();
  
      for (ImmutableMap.Entry<String, String> row : loadStringMap(source).entrySet()) {
        ret.put(Symbol.from(row.getKey()), Symbol.from(row.getValue()));
      }
  
      return ret.build();
    }