'Represent multiple values as dict {value: representation}
@param values: list of values
@param rows: the referenced rows (if values are foreign keys)
@param show_link: render each representation as link
@param include_blank: Also include a blank value
@return: a dict {value: representation}'

def bulk(self, values, rows=None, list_type=False, show_link=True, include_blank=True):

    show_link = (show_link and self.show_link)
    if (show_link and (not rows)):
        rows = self.custom_lookup_rows(None, values)
    self._setup()
    if (rows and self.table):
        values = [row['org_site.site_id'] for row in rows]
    else:
        values = ([values] if (type(values) is not list) else values)
    if values:
        labels = self._lookup(values, rows=rows)
        if show_link:
            link = self.link
            rows = self.rows
            labels = dict(((k, link(k, v, rows.get(k))) for (k, v) in labels.items()))
        for v in values:
            if (v not in labels):
                labels[v] = self.default
    else:
        labels = {}
    if include_blank:
        labels[None] = self.none
    return labels
