/// show help message for command.
show help message for command.
show help message for command .
pub fn show_command_help(&self) {
        println!(
            "Command         : {}\nUsage           : {}\nDescription     : {}",
            self.get_description(),
            self.usage.unwrap_or_else(|| self.name.as_ref()),
            self.about.unwrap_or("")
        );
    }
pub fn show_command_help ( & self ) { println ! ( " \n \n " self get_description ( ) self usage unwrap_or_else ( self name as_ref ( ) ) self about unwrap_or ( " " ) ) ; }
show help message for command.
show help message for command .
&self