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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 check_date_str_format(s, default_time="00:00:00"):
 """Check the format of date string"""

    try:
        str_fmt = s
        if ":" not in s:
            str_fmt = '{} {}'.format(s, default_time)

        dt_obj = datetime.strptime(str_fmt, "%Y-%m-%d %H:%M:%S")

        return RET_OK, dt_obj

    except ValueError:
        error_str = ERROR_STR_PREFIX + "wrong time or time format"
        return RET_ERROR, error_str