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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def load_data(train_path='./data/regression.train', test_path='./data/regression.test'):
    '''
    Load or create dataset
    '''
    print('Load data...')
    df_train = pd.read_csv(train_path, header=None, sep='\t')
    df_test = pd.read_csv(test_path, header=None, sep='\t')
    num = len(df_train)
    split_num = int(0.9 * num)

    y_train = df_train[0].values
    y_test = df_test[0].values
    y_eval = y_train[split_num:]
    y_train = y_train[:split_num]

    X_train = df_train.drop(0, axis=1).values
    X_test = df_test.drop(0, axis=1).values
    X_eval = X_train[split_num:, :]
    X_train = X_train[:split_num, :]

    # create dataset for lightgbm
    lgb_train = lgb.Dataset(X_train, y_train)
    lgb_eval = lgb.Dataset(X_eval, y_eval, reference=lgb_train)

    return lgb_train, lgb_eval, X_test, y_test