A receiver for argument transformers.
Throw an exception indicating that usage was incorrect.
Called after this command's argv is parsed to transform and store the argument's value.
Issue a message that can be shown to the user
Information about this argument for the help output.
Called after all of a command's parameters have been finalized to perform validation of the final value.
The argument that was invoked
The description of this argument.
Optional set of strings to use when the user invokes shell autocomplete on a value for this argument.
Extra information about this argument to pass to the help formatter.
The metavar for this argument.
The number of values that this argument takes.
If true, an error will be thrown if this argument is not given on the command line.