improvements of the pipeline debug views

LINQ/LINQ/Interpreter/Expressions/Keywords/Options/SkipItems.vb

@@ -68,5 +68,9 @@ Namespace Interpreter.Expressions
         Public Overrides Function Exec(context As ExecutableContext) As Object
             Return n.Exec(context)
         End Function
+
+        Public Overrides Function ToString() As String
+            Return $"skip {n}"
+        End Function
     End Class
 End Namespace

LINQ/LINQ/Interpreter/Expressions/Keywords/Options/TakeItems.vb

@@ -69,5 +69,9 @@ Namespace Interpreter.Expressions
         Public Overrides Function Exec(context As ExecutableContext) As Object
             Return n.Exec(context)
         End Function
+
+        Public Overrides Function ToString() As String
+            Return $"take {n}"
+        End Function
     End Class
 End Namespace

LINQ/LINQ/Interpreter/Query/Options.vb

@@ -75,5 +75,9 @@ Namespace Interpreter.Query
             Return raw
         End Function
 
+        Public Overrides Function ToString() As String
+            Return pipeline.JoinBy(" -> ")
+        End Function
+
     End Class
 End Namespace