Parameters not converted properly when using arrays about swifthttp HOT 2 OPEN

extension Array {
    var stringRepresentation: String {
        var str = ""
        self.forEach { str += "\($0)," }
        str = String(str.dropLast()) // drops last comma
        return "[" + str + "]"
    }
}

let strings = ["a", "b", "c"]
let parameters: [String: Any] = [
    "my_array_of_strings": strings.stringRepresentation
]
// will convert to [String: String] = ["my_array_of_strings": "[a,b,c]"]