allColumnsInternal
internal fun ColumnsResolver<*>.allColumnsInternal(removePaths: Boolean = false): TransformableColumnSet<*>
If this is a SingleColumn containing a single ColumnGroup (like SingleColumn<AnyRow> or ColumnsSelectionDsl), it returns a (transformable) ColumnSet containing the children of this ColumnGroup, else it simply returns a (transformable) ColumnSet from this (like when this is a ColumnSet).