Preserve all items after selecting with multiselect widget

Hi, I want to preserve all items after selecting from multiselect widget. For example, with this code:

values = ['a', 'b', 'c']
st.multiselect('test: ', tuple(values), key='1')

after I select ‘a’, the option left to select is ‘b’ and ‘c’. Is it possible to preserve all items (‘a’, ‘b’, ‘c’), after selecting one?

Thank you.