code: public static String[][] additionalContext(final String[] tokens,
        final Map<String, String> prevMap) {
      final String[][] ac = new String[tokens.length][1];
      for (int ti = 0; ti < tokens.length; ti++) {
        final String pt = prevMap.get(tokens[ti]);
        ac[ti][0] = "pd=" + pt;
      }
      return ac;
  
    }
docs: Generated previous decision features for each token based on contents of
  the specified map.
  
  @param tokens
  The token for which the context is generated.
  @param prevMap
  A mapping of tokens to their previous decisions.
  @return An additional context array with features for each token.