Span of GridLayout is not applied in Epoxy

I'm using Epoxy to represent nested recyclerviews.

Other than that, I want to place the inner child(Nested) RecyclerView in GridLayout format, but even if I set span, it only appears in vertical format.

I tried using spanCount and spanSizeOverride (didn't understand what function this is) in Controller to solve it, but it doesn't work.

What's wrong?

This is an example picture and code.

item_parent

<androidx.cardview.widget.CardView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:cardCornerRadius="4dp"
    app:cardElevation="3dp"
    android:layout_margin="10dp">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center">
        <TextView
            android:id="@+id/title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="TEST"
            android:textSize="24sp"
            android:background="@color/gray_400"
            android:layout_marginTop="12dp"
            android:layout_marginLeft="12dp"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintTop_toTopOf="parent" />
        <View
            android:id="@+id/borderline"
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:background="@color/black"
            android:layout_marginTop="12dp"
            app:layout_constraintTop_toBottomOf="@id/title"/>

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/nested_rv"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layout_constraintTop_toBottomOf="@id/borderline"
            android:gravity="center_horizontal"
            app:layoutManager="androidx.recyclerview.widget.GridLayoutManager"
            android:orientation="horizontal" />
        <View
            android:id="@+id/borderline2"
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:background="@color/black"
            android:visibility="gone"
            app:layout_constraintTop_toBottomOf="@id/nested_rv"/>
        <ImageView
            android:id="@+id/expanded"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@id/borderline2"
            app:layout_constraintBottom_toBottomOf="parent"
            android:src="@drawable/ic_arrow_drop_down2"/>
    </androidx.constraintlayout.widget.ConstraintLayout>
</androidx.cardview.widget.CardView>

ParentContoller

class ParentEpoxyController : EpoxyController() {
    private var data : List<ParentItem> = listOf()
            set(value) {
                field = value
                requestModelBuild()
            }

    override fun buildModels() {
        data.forEachIndexed { index, s ->
            ParentDataModel_()
                .id(index)
                .title(s.workout)
                .list(s.list)
                .onBind { model, holder, position ->

                    // Set Nested RV
                    holder.nestedRV.visibility = if(s.isExpandable) View.VISIBLE else View.GONE

                    val controller = ChildEpoxyController()
//                    controller.spanCount = 4// not applied
                    holder.nestedRV.adapter = controller.adapter
                    controller.setItem(data[position].list)

                    holder.expandBtn.setOnClickListener {
                        if(s.isExpandable) {
                            holder.nestedRV.visibility = View.GONE
                            holder.borderline.visibility = View.GONE
                        }
                        else {
                            holder.nestedRV.visibility = View.VISIBLE
                            holder.borderline.visibility = View.VISIBLE

                        }
                        s.isExpandable = !s.isExpandable
                    }
                    requestModelBuild()
                }
                .addTo(this)
        }
    }
}

ChildController

class ChildEpoxyController : EpoxyController() {
    private var data: List<String> = listOf()
            set(value) {
                field = value
                requestModelBuild()
            }
    override fun buildModels() {
        data.forEachIndexed { index, s ->
            ChildDataModel_()
                .id(index)
                .child(s)
                .spanSizeOverride { totalSpanCount, position, itemCount ->
                    4 // span size that i want, but not applied
                }
                .addTo(this)
        }
    }

    fun setItem(list: List<String>) {
        data = list
    }
}