Adapted from django.template.defaultfilters:
    https://github.com/django/django/blob/master/django/template/defaultfilters.py

    Returns a plural suffix if the value is not 1. By default, 's' is used as
    the suffix:

    * If value is 0, vote{{ value|pluralize }} displays "0 votes".
    * If value is 1, vote{{ value|pluralize }} displays "1 vote".
    * If value is 2, vote{{ value|pluralize }} displays "2 votes".

    If an argument is provided, that string is used instead:

    * If value is 0, class{{ value|pluralize:"es" }} displays "0 classes".
    * If value is 1, class{{ value|pluralize:"es" }} displays "1 class".
    * If value is 2, class{{ value|pluralize:"es" }} displays "2 classes".

    If the provided argument contains a comma, the text before the comma is
    used for the singular case and the text after the comma is used for the
    plural case:

    * If value is 0, cand{{ value|pluralize:"y,ies" }} displays "0 candies".
    * If value is 1, cand{{ value|pluralize:"y,ies" }} displays "1 candy".
    * If value is 2, cand{{ value|pluralize:"y,ies" }} displays "2 candies".

def pluralize_dj(value, arg='s'):
    """
    Adapted from django.template.defaultfilters:
    https://github.com/django/django/blob/master/django/template/defaultfilters.py

    Returns a plural suffix if the value is not 1. By default, 's' is used as
    the suffix:

    * If value is 0, vote{{ value|pluralize }} displays "0 votes".
    * If value is 1, vote{{ value|pluralize }} displays "1 vote".
    * If value is 2, vote{{ value|pluralize }} displays "2 votes".

    If an argument is provided, that string is used instead:

    * If value is 0, class{{ value|pluralize:"es" }} displays "0 classes".
    * If value is 1, class{{ value|pluralize:"es" }} displays "1 class".
    * If value is 2, class{{ value|pluralize:"es" }} displays "2 classes".

    If the provided argument contains a comma, the text before the comma is
    used for the singular case and the text after the comma is used for the
    plural case:

    * If value is 0, cand{{ value|pluralize:"y,ies" }} displays "0 candies".
    * If value is 1, cand{{ value|pluralize:"y,ies" }} displays "1 candy".
    * If value is 2, cand{{ value|pluralize:"y,ies" }} displays "2 candies".
    """
    if ',' not in arg:
        arg = ',' + arg
    bits = arg.split(',')
    if len(bits) > 2:
        return ''
    singular_suffix, plural_suffix = bits[:2]

    try:
        if int(value) != 1:
            return plural_suffix
    except ValueError:  # Invalid string that's not a number.
        pass
    except TypeError:  # Value isn't a string or a number; maybe it's a list?
        try:
            if len(value) != 1:
                return plural_suffix
        except TypeError:  # len() of unsized object.
            pass
    return singular_suffix