import pandas as pd
def article_views(views: pd.DataFrame) -> pd.DataFrame:
result1=views[views['author_id']==views['viewer_id']]
result1=sorted(result1['author_id'].unique())
# after the sorted function, the result1 has been turned to list, but the dataframe.
# need to compose a dataframe with result again
result=pd.DataFrame({'id':result1})
return result