Called after this command's argv is parsed and all options are validated to validate the group constraints.
Called after all of a command's parameters have been finalized to perform validation of the final values.
A help message to display for this group.
The name of the group, or null if parameters in the group should not be separated from other parameters in the help output.
If a groupChoice or groupSwitch option is not called on the command line, use the value of the group with a switch or choice name.