write this as:
```
function get_object{T}(builder::GtkBuilder, widgetId::String, _::Type{T}=GtkWidget)
    convert(T, ccall((:gtk_builder_get_object ,libgtk), Ptr{GObjectI},
        (Ptr{GObjectI}, Ptr{Uint8}), builder, bytestring(widgetId)))
end
```
so the user doesn't need to specify the type

However, this makes it redundant with calling `G_.get_object(builder, widget_id)`, so I don't think this is needed at all