code: public void addHeader(String key, Object value) {
  		List<Object> values = headers.get(key);
  		if (values == null) {
  			headers.put(key, values = new ArrayList<Object>());
  		}
  		values.add(value);
  	}
docs: Add a header to the response
  
  @param key The header name
  @param value The header value