code: public static DefaultValueFunction defaultValue(Function function, Object defaultValue) {
  
  		Assert.notNull(function, "Function must not be 'null' for default value operation.");
  		Assert.notNull(defaultValue, "DefaultValue must not be 'null'.");
  
  		return new DefaultValueFunction(function, defaultValue);
  	}
docs: Creates new {@link DefaultValueFunction} representing {@code def(function, defaultValue))}
  
  @param function must not be null
  @param defaultValue must not be null
  @return