def convert_df_2_string(df):
    """
    Convert data frame rows to string output where each new line is defined as \n
    """
    # ititialise string
    output = 'agent,wkt\n'
    for i, row in df.iterrows():
        if i == len(df) - 1:
            output += str(row['label']) + ',' + str(row['geometry'])
        else:
            output += str(row['label']) + ',' + str(row['geometry']) + '\n'
    # set environment variable ${AGENTS}
    # os.environ['AGENTS'] = output
    return output