Nested coroutine stop problem

Foo.cs

class Foo : MonoBehaviour 
{
    Coroutine m_coroutine;

    public void StartThing()
    {
        m_coroutine = StartCoroutine(ParentCoroutine());
    }
    
    public void EndThing()
    {
        if (m_coroutine != null)
        {
            // this stops the parent coroutine, but any ChildCoroutine that was in process will still complete
            StopCoroutine(m_coroutine);
            m_coroutine = null;
        }
    }
    
    public IEnumerator ParentCoroutine()
    {
        yield return ChildCoroutine(1);
        yield return ChildCoroutine(2);
        yield return ChildCoroutine(3);
    }
    
    public IEnumerator ChildCoroutine(float _varyingInput)
    {
        // do stuff based on input
    }
}