Microsoft.ML.Internal.Internallearn namespace requires certain internalization. (#2667)

* Microsoft.ML.Internal.Internallearn namespace requires certain internalization.

* PR feedback.

* PR feedback.

Author: codemzs

src/Microsoft.ML.Data/Dirty/PredictionUtils.cs

@@ -16,7 +16,8 @@ namespace Microsoft.ML.Internal.Internallearn
     /// <summary>
     /// Various utilities
     /// </summary>
-    public static class PredictionUtil
+    [BestFriend]
+    internal static class PredictionUtil
     {
         /// <summary>
         /// generic method for parsing arguments using CommandLine. If there's a problem, it throws an InvalidOperationException, with a message giving usage.
@@ -152,16 +153,4 @@ public static char SepCharFromString(string s)
             }
         }
     }
-
-    /// <summary>
-    /// A generic reverse Comparer (for use in Array.Sort)
-    /// </summary>
-    public sealed class ReverseComparer<T> : IComparer<T>
-        where T : IComparable<T>
-    {
-        public int Compare(T x, T y)
-        {
-            return -x.CompareTo(y);
-        }
-    }
 }

src/Microsoft.ML.Data/Dirty/PredictorInterfaces.cs

@@ -11,12 +11,6 @@
 
 namespace Microsoft.ML.Internal.Internallearn
 {
-
-    /// <summary>
-    /// Signature for loading from a file name.
-    /// </summary>
-    public delegate void SignaturePredictorFromFile(string fileName);
-
     /// <summary>
     /// A generic interface for models that can average parameters from multiple instance of self
     /// </summary>
@@ -146,7 +140,8 @@ internal interface ICanSaveInSourceCode
     /// <summary>
     /// Signature for trainers that produce predictors that in turn can be use to score features.
     /// </summary>
-    public delegate void SignatureFeatureScorerTrainer();
+    [BestFriend]
+    internal delegate void SignatureFeatureScorerTrainer();
 
     /// <summary>
     /// Interface implemented by components that can assign weights to features.

src/Microsoft.ML.Data/Training/EarlyStoppingCriteria.cs

@@ -23,7 +23,7 @@
 
 namespace Microsoft.ML.Internal.Internallearn
 {
-    public delegate void SignatureEarlyStoppingCriterion(bool lowerIsBetter);
+    internal delegate void SignatureEarlyStoppingCriterion(bool lowerIsBetter);
 
     // These criteria will be used in FastTree and NeuralNets.
     public interface IEarlyStoppingCriterion

src/Microsoft.ML.Data/Utilities/SlotDropper.cs

@@ -12,7 +12,8 @@ namespace Microsoft.ML.Internal.Internallearn
     /// <summary>
     /// Drops slots from a fixed or variable sized column based on slot ranges.
     /// </summary>
-    public sealed class SlotDropper
+    [BestFriend]
+    internal sealed class SlotDropper
     {
         private readonly int[] _lengthReduction;