code: public char getPositionKey() {
          String value = Optional.fromNullable(getParameter(SignalParameters.POSITION_KEY.symbol())).or("");
          return value.isEmpty() ? ' ' : value.charAt(0);
      }
docs: Defines a key with the following action. Stop playing the current announcement and resume playing at the beginning of the
  first, last, previous, next, or the current segment of the announcement.
  <p>
  <b>No default. The actions for the position key are fst, lst, prv, nxt, and cur.</b>
  </p>
  
  @return