code: public JBBPOut Utf8(final String str) throws IOException {
      assertNotEnded();
      assertStringNotNull(str);
      if (this.processCommands) {
        this.outStream.write(JBBPUtils.strToUtf8(str));
      }
      return this;
    }
docs: Write chars of a String as encoded Utf8 byte array. There will not be aby information about string length.
  
  @param str a String which bytes should be written as Utf8, must not be null
  @return the DSL session
  @throws IOException it will be thrown for transport errors