code: @Beta
    @Deprecated
    public
    static void append(CharSequence from, File to, Charset charset) throws IOException {
      asCharSink(to, charset, FileWriteMode.APPEND).write(from);
    }
docs: Appends a character sequence (such as a string) to a file using the given character set.
  
  @param from the character sequence to append
  @param to the destination file
  @param charset the charset used to encode the output stream; see {@link StandardCharsets} for
  helpful predefined constants
  @throws IOException if an I/O error occurs
  @deprecated Prefer {@code asCharSink(to, charset, FileWriteMode.APPEND).write(from)}. This
  method is scheduled to be removed in January 2019.