Centering subview with autolayout in viewcontroller

CenteringSubview.swift

fileprivate func createCenterConstraints(with subview: UIView) -> [NSLayoutConstraint]
    {
        var constraints: [NSLayoutConstraint] = [NSLayoutConstraint]()
        let views: [String: Any] = ["view": subview, "superview": self.view]
        
        var horizontalOptions = NSLayoutFormatOptions()
        horizontalOptions.insert(NSLayoutFormatOptions.alignAllCenterY)
        let horizontalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:[superview]-(<=1)-[view]", options: horizontalOptions, metrics: nil, views: views)
        
        var verticalOptions = NSLayoutFormatOptions()
        verticalOptions.insert(NSLayoutFormatOptions.alignAllCenterX)
        let verticalConstraints = NSLayoutConstraint.constraints(withVisualFormat: "V:[superview]-(<=1)-[view]", options: verticalOptions, metrics: nil, views: views)
        
        constraints.append(contentsOf: horizontalConstraints)
        constraints.append(contentsOf: verticalConstraints)
        
        return constraints
    }