docs: public static Object toData(TypedLiteral lit) {
      if (lit == null) throw new IllegalArgumentException("Can't convert null literal");
      Conversion<?> c = uriConversions.get(lit.getDataType());
      if (c == null) throw new IllegalArgumentException("Don't know how to convert literal of type " + lit.getDataType());
      return c.data(lit.getLexical());
    }