Optional (testng 7.9.0 API)

```
@Retention(RUNTIME)
@Target(PARAMETER)
public @interface Optional
```
Specifies that the current parameter is optional. TestNG will pass in a specified default value, or null if none is specified.

- Optional Element Summary
  
  Optional Elements
  Modifier and Type Optional Element Description
  
  java.lang.String value
  The default value to pass to this parameter.

- Element Detail
  - value
```
java.lang.String value
```
    The default value to pass to this parameter.
    The default deserves a bit of explanation. JSR-175 (which defines annotations) says that Java annotation parameters can only be ConstantExpressions, which can be primitive/string literals, but not null.
    In this case, we use this string as a substitute for null; in practice, TestNG will pass null to your code, and not the string "null", if you do not specify a default value here in this parameter.
    
    Returns:
    
    the value (default NULL_VALUE)
    
    Default:
    
    "null"