bels are in a single column of string or integer values representing classs labels
           Example with label_columns=['label'] and text_column='text':
             text|label
             I like this movie.|positive
             I hated this movie.|negative
   3. labels are a single column of numerical values for text regression
      NOTE: Must supply is_regression=True for labels to be treated as numerical targets
             wine_description|wine_price
             Exquisite wine!|100
             W