Merge pull request #1460 from Kotlin/Aleksandr.Nikolaev/column-group-rendering-fix

Improve rendering of ColumnGroup by removing wrapping of column groups by dataFrameOf() in convertToDataFrame()

Author: Allex-Nik

core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/KotlinNotebookPluginUtils.kt

@@ -236,13 +236,13 @@ public object KotlinNotebookPluginUtils {
 
             is FormattedFrame<*> -> dataframeLike.df
 
-            is AnyCol -> dataFrameOf(dataframeLike)
+            is AnyFrame -> dataframeLike
 
             is AnyRow -> dataframeLike.toDataFrame()
 
             is GroupBy<*, *> -> dataframeLike.toDataFrame()
 
-            is AnyFrame -> dataframeLike
+            is AnyCol -> dataFrameOf(dataframeLike)
 
             is DisableRowsLimitWrapper -> dataframeLike.value