anchor.diff:  | @Parameters Field Type | Default Arity | Notes
   | boolean      | 1 |Positional parameters of type `boolean` or `Boolean` require a value. Only `true` or `false` (case insensitive) are valid values.
   | Single-valued type (e.g., `int`, `String`, `File`) | 1 | One parameter required for each position.
  -| Multi-valued type (arrays, collections or maps) | 0..1 | For multi-valued positional parameters (arrays, collections or maps), values are optional, not required.
  +| Multi-valued type (arrays, collections or maps) | 0..1 | For multi-valued positional parameters (arrays, collections or maps), values are optional, not <<Required Parameters,required>>.
   |===
   
   
  
positive.code: ----
  Option `-s` has arity `"1..*"` but instead of consuming all parameters,
  the `-f` argument is recognized as a separate option.
  
  === Default Arity
  If no `arity` is specified, the number of parameters depends on the field's type.
  
negative.code: ----
  
  === Options with an Optional Parameter
  See <<Optional Values>>.
  
  == Argument Groups
  Picocli 4.0 introduces a new `@ArgGroup` annotation and its `ArgGroupSpec` programmatic equivalent.
  