Update app.py

app.py

@@ -19,7 +19,7 @@ with st.sidebar:
     year_list = list(df.Year.unique())[::-1]
     year_list = sorted(year_list)
     
-    selected_year = st.selectbox('Select a year', year_list, index=len(year_list)-1)
+    selected_year = st.selectbox('Select a year', year_list, index=len(year_list)-1).to_string()
 
     cik_list = list(df.CIK.unique())[::-1]
     cik_list = sorted(cik_list)