Create rectangle with rounded corners around multiple containers

We would like to create a rounded rectangle around multiple streamlit containers to (visually) indicate that they are related.

When using streamlit columns, we can achieve this by modifying the styling for the stHorizontalBlock:

st.markdown("""
    <style type="text/css">
    div[data-testid="stHorizontalBlock"] {
        border:10px;
        padding:30px;
        border-radius: 10px;
        background:#FFFFFF;
    }
    </style>
""", unsafe_allow_html=True)

However, this does not allow for grouping of a combination of single and multi column blocks, like:

st.title("Hello World") # we would like to include this in the rounded rectangle
columns = st.columns(2) # the custom css will only be applied to this block
st.dataframe(df) # we would like to include this in the rounded rectangle

We would like to create one rounded rectangle that includes both the title and the next columns

Is there a way to achieve this?