<group>is the group name of commands and
<function>is the function name of the command. An extension may have a set of commands, so typically the group name is the extension name. For example, the ID of the command showing a message of HelloWorld extension is
app.commands.registermethod. The first parameter is the ID of the command and the second is the handler function.
helloworld:show-messagecommand. It can be called manually as follow: