/// <summary>
 /// Initializes the positive only dataset.
 /// </summary>
 private void InitializePositiveOnlyDataset()
 {
     this.positiveOnlyDataset = new PositiveOnlyDataset
     {
         Observations = new List <Tuple <string, string> >
         {
             Tuple.Create("u0", "i0"),
             Tuple.Create("u0", "i1"),
             Tuple.Create("u0", "i4"),
             Tuple.Create("u1", "i3"),
             Tuple.Create("u1", "i4"),
             Tuple.Create("u2", "i2"),
         }
     };
 }
 /// <summary>
 /// Extracts an item from a given instance.
 /// </summary>
 /// <param name="instanceSource">The instance source providing the <paramref name="instance"/>.</param>
 /// <param name="instance">The instance to extract the item from.</param>
 /// <returns>The extracted item.</returns>
 public string GetItem(PositiveOnlyDataset instanceSource, Tuple <string, string> instance)
 {
     return(instance.Item2);
 }
 /// <summary>
 /// Retrieves a list of instances from a given instance source.
 /// </summary>
 /// <param name="instanceSource">The source to retrieve instances from.</param>
 /// <returns>The list of retrieved instances.</returns>
 public IEnumerable <Tuple <string, string> > GetInstances(PositiveOnlyDataset instanceSource)
 {
     return(instanceSource.Observations);
 }