def tb(tb):
    """Transform the tb dataset according to what was found in the explaratory
    analyses, available on sp_np.ipynb

    1. Select only 'journal' and 'year' columns
    2. Rename these two columns to 'Journal' and 'Year', with capitalization
    3. Add a column named 'Source', with all rows = 'TreatmentBank'

    Args:
        tb (pandas.DataFrame): Unchanged dataframe from TreatmentBank processor

    Returns:
        pandas.DataFrame: Transformed tb dataframe
    """
    # Selecting only the columns 'journal' and 'year'
    tb = tb[['journal', 'year']]

    # Renaming columns
    tb.rename(columns={'journal': 'Journal', 'year': 'Year'}, inplace=True)

    # Adding column 'Source', filling all rows = 'TreatmentBank'
    tb['Source'] = 'TreatmentBank'

    return tb