code: @Throws(IllegalNotNullArgumentException.class)
  	public static void isNull(@Nullable final Object reference, @Nullable final String name) {
  		if (reference != null) {
  			throw new IllegalNotNullArgumentException(name, reference);
  		}
  	}
docs: Ensures that a given argument is {@code null}.
  
  Normally, the usage of {@code null} arguments is disregarded by the authors of quality-check. Still, there are
  certain circumstances where null is required, e.g. the primary key of an entity before it is written to the
  database for the first time. In such cases it is ok to use null values and there should also be checks for them.
  For example, to avoid overwriting an existing primary key with a new one.
  
  @param reference
  reference which must be null.
  @param name
  name of object reference (in source code)
  
  @throws IllegalNotNullArgumentException
  if the given argument {@code reference} is not null