object declaring the options the command accepts, or a function accepting and returning a yargs instance
string (or array of strings) that executes this command when given on the command line, first string may contain positional args
boolean (or string) to show deprecation notice
string used as the description for the command in help text, use false for a hidden command
a function which will be passed the parsed argv.
array of strings (or a single string) representing aliases of
exports.command, positional args defined in an alias are ignored