ปีใดที่มีรอบเพลย์ออฟรอบแรกในลีกในร่ม NASL?
What year had a 1st round playoff in the NASL indoor league?
df = pd.DataFrame(columns=['year', 'playoffs', 'league'])
df[(df['playoffs'] == '1st round') & (df['league'] == 'nasl indoor')]['year']