Ambiguous use of 'bytes' ?

Hi,

I am using google direction web service in my application . I want to authenticate url using client id and digital signature. For that i need to use HMAC algorithm .

I tried as given in link : https://github.com/googlemaps/url-signing/blob/gh-pages/URLSigner.swift

import CryptoSwift

class URLSigner: NSObject {
    static func sign(key: String, secret: String) -> URL?{
        let path = "/path/something"
        var secret_key = secret
        secret_key = secret_key.replacingOccurrences(of: "-", with: "+").replacingOccurrences(of: "_", with: "/")
       
        if let decodedData = Data(base64Encoded: secret_key)?.bytes,
        let hmac = try? HMAC(key: decodedData, variant: .sha1).authenticate(Array(path.utf8)), var signature = hmac.toBase64(){
            signature = signature.replacingOccurrences(of: "+", with: "-").replacingOccurrences(of: "/", with: "_")
            return URL(string: "URL" + path + "&signature=" + signature)
        }
        return URL(string: "URL" + path)
}
}

But i am getting error : Ambiguous use of 'bytes' in the below line of code

let decodedData = Data(base64Encoded: secret_key)?.bytes

how to resolve it .

Please help .