init research

dataframe/plugins/expressions-converter/testData/box/any.kt

@@ -0,0 +1,16 @@
+package org.jetbrains.kotlinx.dataframe.explainer
+
+import org.jetbrains.kotlinx.dataframe.*
+import org.jetbrains.kotlinx.dataframe.api.*
+
+object PluginCallback {
+    fun doAction(any: Any) {}
+}
+
+fun box(): String {
+    val a: GroupBy<*, *> = dataFrameOf("a")(1).groupBy("a")
+    a.also {
+        PluginCallback.doAction(it)
+    }
+    return "OK"
+}