code: public Parameters getAsNullableParameters(String key) {
  		AnyValueMap value = getAsNullableMap(key);
  		return value != null ? new Parameters(value) : null;
  	}
docs: Converts map element into an Parameters or returns null if conversion is not
  possible.
  
  @param key a key of element to get.
  @return Parameters value of the element or null if conversion is not
  supported.