         file: String = #fileID,
         function: String = #function,
         line: Int = #line,
+        error: Error? = nil,
         context: [String: CustomStringConvertible] = [:],
         completion: (() -> Void)? = nil
     ) {

    ///   - file: File of the caller.
    ///   - function: Function of the caller.
    ///   - line: Line of the caller.
    ///   - context: Additional meta data.
    ///   - completion: The block to call when log entries sent.
    func warning(

            file: file,
            function: function,
            line: line,
            error: error,
            context: context,
            completion: completion
        )
