How to insert elements out of order?
You can use the st.empty method as a placeholder,
to "save" a slot in your app that you can use later.
```python
st.text('This will appear first')
Appends some text to the app.
my_slot1 = st.empty()
Appends an empty slot to the app. We'll use this later.
my_slot2 = st.empty()
Appends another empty slot.
st.text('This will appear last')
Appends some more text to the app.
my_slot1.text('This will appear second')
Replaces the first empty slot with a text string.
my_slot2.line_chart(np.random.randn(20, 2))
Replaces the second empty slot with a chart.
```
