def train_classifier(train_df, clf):
    """Train classifier

    :param train_df: Train dataframe
    :param clf: Classifier
    """
    features = list(train_df.columns.difference(['Drug', 'Disease', 'Class']))
    X = train_df[features]
    print("Dataframe sample of training X (train_classifier features):")
    print(X.head())
    y = train_df['Class']
    print(y.head())
    print('📦 Fitting classifier...')
    clf.fit(X, y)
    return clf