extension Kingfisher where Base == String {
    public var md5: String {
        if let data = base.data(using: .utf8, allowLossyConversion: true) {
            var byteBuffer: [UInt8] = []
            data.withUnsafeBytes {
                byteBuffer.append(contentsOf: $0)
            let MD5Calculator = MD5(byteBuffer)
            let MD5Data = MD5Calculator.calculate()
            var MD5String = String()
            for c in MD5Data {
                MD5String += String(format: "%02x", c)
            return MD5String
        } else {
            return base