Terminal pivot operations return incorrect `T` schema, should be Any? instead

[koperagen]

result of pivot is always new set of columns created based on data in columns. Current return type is a guaranteed runtime exception:

Operations like public fun <T> Pivot<T>.count(): DataRow<T> = delegate { count() } should become

public fun <T> Pivot<T>.count(): DataRow<*> = delegate { count() }

students.json

import org.jetbrains.kotlinx.dataframe.DataFrame
import org.jetbrains.kotlinx.dataframe.annotations.*
import org.jetbrains.kotlinx.dataframe.api.*
import org.jetbrains.kotlinx.dataframe.io.*

@DataSchema
data class Students(
    val age: Int,
    val name: Name,
    val scores: List<Scores>
) {
    @DataSchema
    data class Name(
        val firstName: String,
        val lastName: String?
    )

    @DataSchema
    data class Scores(
        val subject: String,
        @ColumnName("value")
        val `value`: Int
    )
}

fun main() {
    val students = DataFrame.readJson("/home/nikita/IdeaProjects/dataframe-examples/students.json")
        .cast<Students>()

    students.explode { scores }.pivot { scores.subject }.count().schema().print()
}

=>

math: Int
biology: Int
music: Int
nothing: Int
russian: Int
art: Int

There's some connection to original data if "with" is used, but even so it's still misleading. As a side note,

students.explode { scores }.pivot { scores.subject }.with { it }.schema().print()

math: *
    name:
        firstName: String
        lastName: String
    age: Int
    scores:
        subject: String
        value: Int

biology: *
    name:
        firstName: String
        lastName: String
    age: Int
    scores:
        subject: String
        value: Int

music:
    name:
        firstName: String
        lastName: String
    age: Int
    scores:
        subject: String
        value: Int

nothing:
    name:
        firstName: String
        lastName: String?
    age: Int
    scores:
        subject: String
        value: Int

russian:
    name:
        firstName: String
        lastName: String
    age: Int
    scores:
        subject: String
        value: Int

art:
    name:
        firstName: String
        lastName: String
    age: Int
    scores:
        subject: String
        value: Int