import re


def find_timestamp(text_list):
    """
    Find timestamp line and put digit's value

    Parameters
    ----------
    text_list : dataframe
        A dataframe you want to convert

    Returns
    -------
    dataframe
        it has new columns ["start_timestamp", "digit"]
        The digit column helps filling start_timestamp and end_timestamp
    """
    pat = re.compile('(\d\d:\d\d:\d\d. *\d\d)')
    matches = pat.search(text_list['speech'])
    if matches is not None:
        text_list['start_timestamp'] = matches.group(1) if matches is not None else None
        text_list['digit'] = 1
    else:
        text_list['digit'] = 0
        text_list['start_timestamp'] = None

    return(text_list)