gainNone

In decision tree algorithms, "gainNone" indicates that no specific criterion is used to select the best attribute for splitting the data at a node. Essentially, it means that the model isn't attempting to improve its accuracy by choosing different features to divide the data further. Instead, it might keep the current splits as they are, without trying to optimize the separation of groups within the data. This setting is useful if you want the tree to remain simple or when other criteria are used externally to influence the splitting process.