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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def read_wwln(file):
 """Read WWLN file"""

    tmp = pd.read_csv(file, parse_dates=True, header=None,
                      names=['date', 'time', 'lat', 'lon', 'err', '#sta'])
    # Generate a list of datetime objects with time to miliseconds
    list_dts = []
    for dvals, tvals, in zip(tmp['date'], tmp['time']):
        list_dts.append(gen_datetime(dvals, tvals))
    dtdf = pd.DataFrame(list_dts, columns=['datetime'])
    result = pd.concat([dtdf, tmp], axis=1)
    result = result.drop(['date', 'time'], axis=1)
    return result