Transforms a written month into corresponding month number.

    E.g. November -> 11, or May -> 05.

    Keyword arguments:
    datestring -- a string

    Returns:
    String, or None if the transformation fails

def get_month(datestring):
    """Transforms a written month into corresponding month number.

    E.g. November -> 11, or May -> 05.

    Keyword arguments:
    datestring -- a string

    Returns:
    String, or None if the transformation fails
    """
    convert_written = re.compile(r"jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec", re.IGNORECASE)
    month = convert_written.search(datestring)
    month_number = None

    # If there's a match, convert the month to its corresponding number
    if month:
        month_number = strptime(month.group(), "%b").tm_mon
        if month_number < 10:
            month_number = add_zero(month_number)

    return str(month_number)