old_contents: from . import fns
  from . import node
  from . import tree
  
  from .fns import (transform_root_node,
                    transform_node_data,
                    transform_root_node_postwalk,
                    transform_node_data_postwalk)
  from .node import (remove_dropout,
                     replace_node,
                     update_hyperparameters)
  from .tree import (remove_nodes,
                     remove_subtree,
                     remove_parent,
                     add_parent,
                     add_hyperparameters,
                     remove_parents,
                     move_node)
  
new_contents: from . import fns
  from . import node
  from . import tree
  
  from .fns import (transform_root_node,
                    transform_node_data,
                    transform_root_node_postwalk,
                    transform_node_data_postwalk)
  from .node import (remove_nodes_with_class,
                     remove_dropout,
                     replace_node,
                     update_hyperparameters)
  from .tree import (remove_nodes,
                     remove_subtree,
                     remove_parent,
                     add_parent,
                     add_hyperparameters,
                     remove_parents,
                     move_node)
  
subject: add remove_nodes_with_class to init