     /// - Parameters:
     ///   - closure: The closure to be called on failure.
     /// - Returns: `self` to enable consecutive method calls (e.g. `importer.startImportingRecords {...}.onProgress {...}`).
-    open func onFail(_ closure: @escaping () -> Void) -> Self {
+    public func onFail(_ closure: @escaping () -> Void) -> Self {
         self.failClosure = closure
         return self
     }

    /// - Parameters:
    ///   - closure: The closure to be called on progress. Takes the current count of imported lines as argument.
    /// - Returns: `self` to enable consecutive method calls (e.g. `importer.startImportingRecords {...}.onProgress {...}`).
    open func onProgress(_ closure: @escaping (_ importedDataLinesCount: Int) -> Void) -> Self {
        self.progressClosure = closure
        return self
    }

    ///
    /// - Parameters:
    ///   - closure: The closure to be called on finish. Takes the array of all imported records mapped to as its argument.
    public func onFinish(_ closure: @escaping (_ importedRecords: [T]) -> Void) {
        self.finishClosure = closure
    }

