init research

dataframe/plugins/kotlin-dataframe/testData/box/dataFrameOf_nested.kt

@@ -0,0 +1,20 @@
+import org.jetbrains.kotlinx.dataframe.*
+import org.jetbrains.kotlinx.dataframe.annotations.*
+import org.jetbrains.kotlinx.dataframe.api.*
+import org.jetbrains.kotlinx.dataframe.io.*
+
+fun box(): String {
+    val df = dataFrameOf(
+        "a" to columnOf("1"),
+        "b" to columnOf(
+            "c" to columnOf("2"),
+        ),
+        "d" to columnOf(dataFrameOf("a")(123)),
+        "gr" to listOf("1").toDataFrame().asColumnGroup(),
+    )
+    val str: DataColumn<String> = df.a
+    val str1: DataColumn<String> = df.b.c
+    val i: DataColumn<Int> = df.d[0].a
+    val str2: DataColumn<String> = df.gr.value
+    return "OK"
+}