retrieves siren list from input xlsx and batches get() to output xlsx

def batch(in_xlsx, out_xlsx):
    '''
        retrieves siren list from input xlsx and batches get() to output xlsx
    '''
    import pandas as pd
    import time
    import openpyxl
    pd.core.format.header_style = None

    # load file
    sirens_df = pd.read_excel(in_xlsx)

    # extract and batch sirens
    sirens_sr = sirens_df[sirens_df.columns[0]]
    sirens = [get(siren) for siren in sirens_sr]
    sirens = [str(siren).zfill(9) for siren in sirens] # <-- repair leading zeros

    # convert to dataframe and merge with initial sirens
    res = pd.DataFrame(sirens)
    final = pd.concat([sirens_df, res], axis=1)

    # save to xlsx
    tmstmp = time.strftime('%Y%m%d')
    final.to_excel(out_xlsx, sheet_name='{} results'.format(tmstmp))
    
    return 'export ok'