ผู้ดำรงตำแหน่งประชาธิปไตยคนใดมาจากเขตโอไฮโอ 7
Which democratic incumbent is from the district of ohio 7?
df = pd.DataFrame(columns=['incumbent', 'party', 'district'])
df[(df['party'] == 'democratic') & (df['district'] == 'ohio 7')]['incumbent']