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public class FirstClass {
    fileprivate func someMethod() {}
}
 
internal class BusinessClass: FirstClass {
    override internal func someMethod() {}
}

private class Tax {
    

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import UIKit
 
final class Slider: UISlider {
 
}

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import UIKit
 
final class Slider: UISlider {
 
    override func draw(_ rect: CGRect) {
        super.draw(rect)
        setup()
    }
 
    private func setup() {

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final class Slider: UISlider {
 
    private let baseLayer = CALayer() // Step 3
 
    override func draw(_ rect: CGRect) {
        super.draw(rect)
        setup()
    }
 

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// Step 4
final class ThumbView: UIView {
 
    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }
 
    required init?(coder: NSCoder) {
        super.init(coder: coder)

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// Step 4
extension UIView {
 
    var snapshot: UIImage {
        let renderer = UIGraphicsImageRenderer(bounds: bounds)
        let capturedImage = renderer.image { context in
            layer.render(in: context.cgContext)
        }
        return capturedImage
    }

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// Step 5
private func createThumbImageView() {
    let thumbSize = (3 * frame.height) / 4
    let thumbView = ThumbView(frame: .init(x: 0, 
                                           y: 0, 
                                           width: thumbSize, 
                                           height: thumbSize))
    thumbView.layer.cornerRadius = thumbSize / 2
    let thumbSnapshot = thumbView.snapshot
    setThumbImage(thumbSnapshot, for: .normal)

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// Step 5
private func createThumbImageView() {
    let thumbSize = (3 * frame.height) / 4
    let thumbView = ThumbView(frame: .init(x: 0, 
                                           y: 0, 
                                           width: thumbSize, 
                                           height: thumbSize))
    thumbView.layer.cornerRadius = thumbSize / 2
    let thumbSnapshot = thumbView.snapshot
    setThumbImage(thumbSnapshot, for: .normal)

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private let trackLayer = CAGradientLayer() // Step 7

// Step 7
private func configureTrackLayer() {
    let firstColor = UIColor(red: 210/255, green: 152/255, blue: 238/255, alpha: 1).cgColor
    let secondColor = UIColor(red: 166/255, green: 20/255, blue: 217/255, alpha: 1).cgColor
    trackLayer.colors = [firstColor, secondColor]
    trackLayer.startPoint = .init(x: 0, y: 0.5)
    trackLayer.endPoint = .init(x: 1, y: 0.5)
    trackLayer.frame = .init(x: 0, 

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private func setup() {
    clear()
    createBaseLayer() // Step 3
    createThumbImageView() // Step 5
    configureTrackLayer() // Step 7
    addTarget(self, action: #selector(valueChanged(_:)), for: .valueChanged) // Step 8
}

// Step 8
@objc private func valueChanged(_ sender: Slider) {