-                                       #TODO: see if we can't prevent key normalisation with ->normalizeKeys(false)
-                                       #->scalarNode('roots')->cannotBeEmpty()->defaultValue($defaults['roots'])->end()
-                                       ->variableNode('roots')
-                                               ->treatNullLike([])
-                                               ->defaultValue($defaults['roots'])
-                                               #->scalarPrototype()->end()
-                                       ->end()