         if row >= nRows {
             return Bit.Zero
         }
-        var newContents: [T] = []
+        var newContents = [T]()
         let beforeRow = contents[0..<(row * nCols)]
         let afterRow = contents[((row + 1) * nCols)..<(nRows * nCols)]
         newContents.appendContentsOf(beforeRow)

    */
    public var edges: [(Vertex, Vertex)] {
        get {
            var result: [(Vertex, Vertex)] = []
            for row in 0..<size {
                for col in row..<size {
                    if matrix[row, col] == 1{

            throw GraphError.VertexNotPresent
        }

        var result = [Vertex]()

        for row in 0..<size {
            if matrix[row, index] == 1 {
