unecesssary "get_class" checks
As far as I can tell, you can't mix State nodes with other types, plus _get_configuration_warning() already warns about any non-State children so are these type checks really necessary?
https://gitlab.com/atnb/xsm/-/blob/b66750c9746fd60e4d3849b7047228837647499a/addons/xsm/state.gd#L374
https://gitlab.com/atnb/xsm/-/blob/b66750c9746fd60e4d3849b7047228837647499a/addons/xsm/state.gd#L396
https://gitlab.com/atnb/xsm/-/blob/b66750c9746fd60e4d3849b7047228837647499a/addons/xsm/state.gd#L406
https://gitlab.com/atnb/xsm/-/blob/b66750c9746fd60e4d3849b7047228837647499a/addons/xsm/state.gd#L464
https://gitlab.com/atnb/xsm/-/blob/b66750c9746fd60e4d3849b7047228837647499a/addons/xsm/state.gd#L470
https://gitlab.com/atnb/xsm/-/blob/b66750c9746fd60e4d3849b7047228837647499a/addons/xsm/state.gd#L480
https://gitlab.com/atnb/xsm/-/blob/b66750c9746fd60e4d3849b7047228837647499a/addons/xsm/state.gd#L503
https://gitlab.com/atnb/xsm/-/blob/b66750c9746fd60e4d3849b7047228837647499a/addons/xsm/state.gd#L510
https://gitlab.com/atnb/xsm/-/blob/b66750c9746fd60e4d3849b7047228837647499a/addons/xsm/state.gd#L518