ProcedureKit compilation error

JSONSerializationProcedure.swift

public final class JSONSerializationProcedure<T: JSONObject>: Procedure, ResultInjection {

    public var requirement: PendingValue<URLRequest> = .pending
    public var result: PendingValue<HTTPRequirement<Data>> = .pending

    private var object: ResourceResult<T>

    public init(object:  ResourceResult<T>) {
        self.object = object
        super.init()
    }

    public override func execute() {
        guard let require = requirement.value else {
            finish(withError: ProcedureKitError.requirementNotSatisfied())
            return
        }

        var anyData: Any?

        switch object {
        case let .singleton(value):
            anyData = value.JSON
        case let .collection(objects):
            anyData = objects.flatMap{ $0.JSON }
        }

        guard let finalObject = anyData else {
            finish(withError: MediaServerAPIError.SerializingError.marshal)
            return
        }

        do {
            let data = try JSONSerialization.data(withJSONObject: finalObject, options: [])
            result = .ready(HTTPRequirement(payload: data, request: require))
            finish()
        } catch let error {
            finish(withError: error)
        }

    }