Improvements to train function and predict function #580
Description
There are suggestions in the process of using the split data function to distinguish training data from test data and to use training functions and predictive functions.
When creating a train function, it is very convenient to take train_table data of split data by default.
In the predict function, however, it is initialized as train_table data, so it needs to be changed to test data every time.
Therefore, it seems to be much easier to set the initial value of test_table to default value in the predict function.