code: public Map<String, List<String>> getResponseHeaders() {
  		if (myResponseHeaders == null) {
  			myResponseHeaders = new HashMap<>();
  		}
  		return myResponseHeaders;
  	}
docs: Returns a map containing any headers which should be added to the outgoing
  response. This methos creates the map if none exists, so it will never
  return <code>null</code>
  
  @since 2.0 (note that this method existed in previous versions of HAPI but the method
  signature has been changed from <code>Map&lt;String, String[]&gt;</code> to <code>Map&lt;String, List&lt;String&gt;&gt;</code>