def dictlist_convert_to_datetime(dict_list: Iterable[Dict],
                                 key: str,
                                 datetime_format_string: str) -> None:
    """
    Process an iterable of dictionaries. For each dictionary ``d``, convert
    (in place) ``d[key]`` to a ``datetime.datetime`` form, using
    ``datetime_format_string`` as the format parameter to
    :func:`datetime.datetime.strptime`.
    """
    for d in dict_list:
        d[key] = datetime.datetime.strptime(d[key], datetime_format_string)