code: public static synchronized Object putAdditionalState(String key, Object value) {
  		return additionalState.put(key, value);
  	}
docs: When a mock framework API needs to store additional state not applicable
  for the other methods, it may use this method to do so.
  
  @param key
  The key under which the <tt>value</tt> is stored.
  @param value
  The value to store under the specified <tt>key</tt>.
  @return The previous object under the specified <tt>key</tt> or
  {@code null}.