PR review comments

Author: sfilipi

docs/samples/Microsoft.ML.Samples/Dynamic/Transforms/Conversion/MapKeyToVectorMultiColumn.cs

@@ -5,7 +5,7 @@
 
 namespace Samples.Dynamic
 {
-    class MapKeyToVectorMultiColumn
+    public class MapKeyToVectorMultiColumn
     {
         /// This example demonstrates the use of MapKeyToVector by mapping keys to floats[] for multiple columns at once. 
         /// Because the ML.NET KeyType maps the missing value to zero, counting starts at 1, so the uint values
@@ -30,10 +30,10 @@ public static void Example()
             var data = mlContext.Data.LoadFromEnumerable(rawData);
 
             // Constructs the ML.net pipeline
-            var pipeline = mlContext.Transforms.Conversion.MapKeyToVector(
-                new[]{
-                new InputOutputColumnPair ("TimeframeVector", "Timeframe"),
-                new InputOutputColumnPair ("CategoryVector", "Category") });
+            var pipeline = mlContext.Transforms.Conversion.MapKeyToVector(new[]{
+                    new InputOutputColumnPair ("TimeframeVector", "Timeframe"),
+                    new InputOutputColumnPair ("CategoryVector", "Category")
+            });
 
             // Fits the pipeline to the data.
             IDataView transformedData = pipeline.Fit(data).Transform(data);
@@ -44,7 +44,7 @@ public static void Example()
 
             Console.WriteLine($" Timeframe           TimeframeVector         Category    CategoryVector");
             foreach (var featureRow in features)
-                Console.WriteLine($"{featureRow.Timeframe}\t\t\t{string.Join(',', featureRow.TimeframeVector)}\t\t\t{featureRow.Category}\t\t{string.Join(',', featureRow.CategoryVector)}");
+                Console.WriteLine($"{featureRow.Timeframe}     {string.Join(',', featureRow.TimeframeVector)}   {featureRow.Category}      {string.Join(',', featureRow.CategoryVector)}");
 
             // TransformedData obtained post-transformation.
             //

src/Microsoft.ML.Data/Data/SchemaDefinition.cs

@@ -32,8 +32,10 @@ public KeyTypeAttribute()
         }
 
         /// <summary>
-        /// Marks member as <see cref="KeyDataViewType"/>. The <paramref name="count"/> should be set to
-        /// one more than the maximum value for the keys (to account for missing values).
+        /// Marks member as <see cref="KeyDataViewType"/> and specifies <see cref="KeyDataViewType"/> cardinality.
+        /// In case of the attribute being used with int types, the <paramref name="count"/> should be set to one more than
+        /// the maximum value to account for counting starting at 1 (0 is reserved for the missing KeyType). E.g the cardinality of the
+        /// 0-9 range is 10.
         /// If the values are outside of the specified cardinality they will be mapped to the missing value representation: 0.
         /// </summary>
         /// <param name="count">Cardinality of <see cref="KeyDataViewType"/>.</param>