get
Gets the argument associated with this command.
The argument provides additional data or context required for the command's execution. Its format and meaning are specific to the command defined by getName. For some commands, an argument may not be necessary, in which case this method might return null or an empty string.
Examples of arguments:
- For a "NAVIGATE" command, the argument could be a URL or a screen ID.
- For a "SET_VOLUME" command, the argument could be a numerical value (as a string).
- For a "SHOW_MESSAGE" command, it could be the text of the message.
Return
A string representing the command argument, or null if the command does not require an argument or if no argument is provided.