Convert ColumnPathApproximation to typealias

 Makes it easier to call df methods with ColumnPath parameters

Author: koperagen

plugins/kotlin-dataframe/src/org/jetbrains/kotlinx/dataframe/plugin/impl/api/flatten.kt

@@ -28,7 +28,7 @@ class Flatten0 : AbstractSchemaModificationInterpreter() {
     val Arguments.columns: ColumnsResolver by arg()
 
     override fun Arguments.interpret(): PluginDataFrameSchema {
-        val columns = columns.resolve(receiver).map { pathOf(*it.path.path.toTypedArray()) }
+        val columns = columns.resolve(receiver).map { it.path }
         return receiver
             .asDataFrame()
             .flatten(keepParentNameForColumns, separator) { columns.toColumnSet() }

plugins/kotlin-dataframe/src/org/jetbrains/kotlinx/dataframe/plugin/impl/api/move.kt

@@ -25,7 +25,7 @@ class ToTop : AbstractSchemaModificationInterpreter() {
     val Arguments.receiver: MoveClauseApproximation by arg()
 
     override fun Arguments.interpret(): PluginDataFrameSchema {
-        val columns = receiver.columns.resolve(receiver.df).map { pathOf(*it.path.path.toTypedArray()) }
+        val columns = receiver.columns.resolve(receiver.df).map { it.path }
         return receiver.df.asDataFrame().move { columns.toColumnSet() }.toTop().toPluginDataFrameSchema()
     }
 }

plugins/kotlin-dataframe/src/org/jetbrains/kotlinx/dataframe/plugin/impl/data/ColumnPathApproximation.kt

@@ -1,3 +1,5 @@
 package org.jetbrains.kotlinx.dataframe.plugin.impl.data
 
-data class ColumnPathApproximation(val path: List<String>)
+import org.jetbrains.kotlinx.dataframe.columns.ColumnPath
+
+typealias ColumnPathApproximation = ColumnPath