def prettify_date(date_string):
    """
    This function receives a string representing a date, for example 2018-07-28T10:47:55.000Z.
    It returns the same date in a readable format - for example, 2018-07-28 10:47:55.
    """
    date_string = date_string[:-5]  # remove the .000z at the end
    date_prettified = date_string.replace("T", " ")
    return date_prettified