get_action_parameter_type

Queries the type of the parameter that must be given when activating the named action within this.

When activating the action using [method@Gio.ActionGroup.activate_action], the [type@GLib.Variant] given to that function must be of the type returned by this function.

In the case that this function returns `NULL`, you must not give any [type@GLib.Variant], but `NULL` instead.

The parameter type of a particular action will never change but it is possible for an action to be removed and for a new action to be added with the same name but a different parameter type.

Parameters:

this	a [type@Gio.ActionGroup]
action_name	the name of the action to query

Returns:

the parameter type