from datetime import datetime


def create_date_time_string() -> str:
    """
    Creates a string consisting of YYYY_MM_DD__hh_mm_ss, where Y represents numbers of the current year, M represents
    numbers of the current month, D represents numbers of the current day, h represents numbers of the current hour, m
    represents numbers of the current minute and s represents numbers of the current seconds.

    Returns
    -------
    now: Generated string from the current date and time.
    """

    now = str(datetime.now()).replace('-', '_').replace(':', '_').replace(' ', '__')[0:20]
    return now