แสดงชื่อมณฑลที่มีผู้แทนอย่างน้อยสองคน
Show the names of counties that have at least two delegates.
df_election = pd.DataFrame(columns=['District']); df_county = pd.DataFrame(columns=['County_name', 'County_id'])
df_county[df_county['County_id'].isin(df_election['District'].value_counts()[df_election['District'].value_counts() >= 2].index)]['County_name']