I am currently trying to apply Linear Regression model to test the relationship between two variables $X$ and $Y$. Given a dataset with $8$ columns and $1000$ rows, I want to split this dataset into training and test sets using split_train_test. But i wonder what is the difference between split_train_test(dataset, test_size, random_test = int) vs split_train_test(dataset, test_size).Also, does the 2nd one (without setting random_test=int) give me a different test set and training set each time I re-run my program? Does the 1st one give me the same test set and training set every time I re-run my program? What is the difference between setting random_test=42 vs random_test=43, for example?