def drop_unneeded_cols(df_adverse_ev):
    """ Drop the columns that will not be used as features """
    drop_cols = ['companynumb','duplicate', 'occurcountry',
                 'patient', 
                 'primarysourcecountry', 'receiptdateformat',
                 'receiver', 'receivedate', 'receivedateformat', 'reportduplicate',
                 'reporttype','safetyreportid',
                 'safetyreportversion', 'sender',
                 'transmissiondate','transmissiondateformat']
    df_adverse_ev = df_adverse_ev.drop(drop_cols, axis=1)
    return df_adverse_ev