Add curve on arc swift

I want to generate a curve in the middle of a line programatically, however the edge of the curve is not rounded using my current solution.

func createPath() -> CGPath {
    let height: CGFloat = 86.0
    let path = UIBezierPath()
    let centerWidth = self.frame.width / 2
    path.move(to: CGPoint(x: 0, y: 0))
    path.addLine(to: CGPoint(x: (centerWidth - (height/2)), y: 0))
    path.addArc(withCenter: CGPoint(x: centerWidth, y: 0), radius: 80 / 2, startAngle: 180 * CGFloat(PI)/180, endAngle: 0 * CGFloat(PI)/180, clockwise: false)
    path.addLine(to: CGPoint(x: self.frame.width, y: 0))
    path.addLine(to: CGPoint(x: self.frame.width, y: self.frame.height))
    path.addLine(to: CGPoint(x: 0, y: self.frame.height))
    path.lineCapStyle = .round
    path.stroke()
    path.close()
    self.path = path
    return path.cgPath
}

This is the Arc I have created but I want the curves to be rounded:

But I want it to be like this:

You can just draw more arc like you already does. Or may be you can use path.addCurve, if you dont want oval

    func createPath() -> CGPath {
        let bigRadius: CGFloat = 40.0
        let path = UIBezierPath()
        let centerWidth = self.frame.width / 2
        path.move(to: CGPoint(x: 0, y: 0))
        let radius: CGFloat = 4 //change it if you want
        let leftArcOriginX = centerWidth - bigRadius - radius
        let leftArcOriginY: CGFloat = 0
        path.addLine(to: CGPoint(x: leftArcOriginX, y: leftArcOriginY))
        // add left little arc, change angle if you want, if you dont want oval, may be you can use path.addCurve(to: , controlPoint1: , controlPoint2: )
        path.addArc(withCenter: CGPoint(x: leftArcOriginX, y: leftArcOriginY + radius), radius: radius, startAngle: CGFloat(270.0 * Double.pi/180.0), endAngle: 0, clockwise: true)
        // add big arc
        path.addArc(withCenter: CGPoint(x: centerWidth, y: radius), radius: bigRadius, startAngle: CGFloat(180.0 * Double.pi/180.0), endAngle: CGFloat(0 * Double.pi/180.0), clockwise: false)
        // add right litte arc
        path.addArc(withCenter: CGPoint(x: centerWidth + bigRadius + radius, y: radius), radius: radius, startAngle: CGFloat(180.0 * Double.pi/180.0), endAngle: CGFloat(270.0 * Double.pi/180.0), clockwise: true)
        path.addLine(to: CGPoint(x: self.frame.width, y: 0))
        path.addLine(to: CGPoint(x: self.frame.width, y: self.frame.height))
        path.addLine(to: CGPoint(x: 0, y: self.frame.height))
        path.lineCapStyle = .round
        path.stroke()
        path.close()
        return path.cgPath
    }