A peas.Engine, or NULL.
the extension GType
the name of the first property.
the value of the first property, followed optionally by more name/value pairs, followed by NULL.
a new instance of peas.ExtensionSet
ConstructionException GTK+ fails to create the object.
Create a new peas.ExtensionSet for the exten_type extension type.
If engine is NULL, then the default engine will be used.
Since libpeas 1.22, exten_type can be an Abstract GType and not just an Interface GType
See ExtensionSet.new for more information.