Select All Feature in st.selectbox

I am attempting to plot a scatter plot using altair on streamlit.

I am having trouble with the selectbox which contains each US state. Before touching the selectbox all the states are displayed on the chart, however when I choose one specific state to focus on using selectbox I can’t go back to select all unless I remove the dropdown the page. Is there a way I can select all values using a dropdown with having to do it manually using multiselect?

states_list = list(df_w.State.unique())
state_dropdown = st.sidebar.selectbox('State',states_list)

[DhruvkBhatt]

import streamlit as st

states_list = ['Alabama','New York','Texas','Washington']
l2=[]
l2=states_list[:]
l2.append('Select all')
state_dropdown = st.multiselect('State',l2)

if 'Select all' in state_dropdown :
	state_dropdown=states_list
	
st.write(state_dropdown)

[DhruvkBhatt]

@sammyhajomar and @nthmost Done