data = fetch_openml(name='adult', version=2, as_frame='auto')
#create target and prediction
df['target'] = df['education-num']
df['prediction'] = df['education-num'].values + np.random.normal(0, 6, df.shape[0])
#split data into reference and current
ref = df[~df.education.isin(['Some-college', 'HS-grad', 'Bachelors'])]
curr = df[df.education.isin(['Some-college', 'HS-grad', 'Bachelors'])]