 Darrick Bachman และ Brett Varon กำกับและเขียนบททั้งหมดกี่ตอน
How many episodes have been directed and written by Darrick Bachman and Brett Varon? 
df = pd.DataFrame([], columns=['directed_by', 'written_by'])
df[df['written_by'] == 'Darrick Bachman and Brett Varon']['directed_by'].count()