MainSDK.swift

// MainSDK
public class NumberInspector {
    public weak var delegate: NumberInspectorDelegate?
    
    // ...
    
    public func inspect(number: Int) {
        // perform  inspection and notify delegate when done
    }
}

public protocol NumberInspectorDelegate: class {
    func didFinishInspecting(number: Int, foundFeatures: [String])
}