Ансамбль деревьев

function mse_alt(trees, X, y)
    n_features = size(X, 2)
    n_samples = size(X, 1)
    importance = zeros(n_features)
    for tree in trees
        try
            if isdefined(DecisionTree, :importance)
                tree_imp = DecisionTree.importance(tree)
                if length(tree_imp) == n_features
                    importance += tree_imp
                end
            else
                tree_imp = zeros(n_features)
                function traverse(node, weight=1.0)
                    if !node.isleaf
                        feat_id = node.feat_id
                        if !isnothing(feat_id) && feat_id > 0 && feat_id <= n_features
                            n_node = node.n
                            impurity_reduction = node.score - 
                                                (node.left.n / n_node) * node.left.score - 
                                                (node.right.n / n_node) * node.right.score
                            tree_imp[feat_id] += impurity_reduction * (n_node / n_samples)
                            traverse(node.left)
                            traverse(node.right)
                        end
                    end
                end
                
                traverse(tree)
                importance += tree_imp
            end
        catch e
            continue
        end
    end
    
    if sum(importance) > 0
        importance = importance / sum(importance)
    end
    
    return importance
end