def get_database_data(file_name='<STR_LIT>'):
if not os.path.exists(file_name):<EOL><INDENT>raise IOError("<STR_LIT>".format(file_name))<EOL><DEDENT>df = pd.read_csv(file_name, header=<NUM_LIT:1>)<EOL>return df<EOL>
return the energy (eV) and Sigma (barn) from the file_name

    Parameters:
    ===========
    file_name: string ('' by default) name of csv file

    Returns:
    ========
    pandas dataframe

    Raises:
    =======
    IOError if file does not exist