HTMLCalendar显示为字符串，而不是正确使用HTML (Django)

from django.utils.safestring import mark_safe
from django.contrib.sites.shortcuts import get_current_site
from django.urls import reverse
from django.contrib.auth.models import User
from django.contrib.auth import get_user_model
from django.contrib.auth.tokens import default_token_generator
from django.core.mail import send_mail
from django.template.loader import render_to_string
from django.utils.http import urlsafe_base64_encode, urlsafe_base64_decode
from django.utils.encoding import force_bytes, force_text

from datetime import datetime
from calendar import HTMLCalendar
from django.urls import reverse


class MyCalendar(HTMLCalendar):
    def __init__(self, events):
        super().__init__()
        self.events = events

    def formatday(self, day, weekday, year, month):
        if day != 0:
            cssclass = self.cssclasses[weekday]
            if date.today() == date(year, month, day):
                cssclass += ' today'
            if day in self.events:
                cssclass += ' filled'
                body = ['<ul class="event-list">']
                for event in self.events[day]:
                    body.append(f'<li>{event}</li>')
                body.append('</ul>')
                return self.day_cell(cssclass, f'<span class="day-number">{day}</span><div class="event">{"".join(body)}</div>')
            return self.day_cell(cssclass, f'<span class="day-number">{day}</span>')
        return self.day_cell('noday', '&nbsp;')

    def formatmonth(self, year, month):
        self.year, self.month = year, month
        return super().formatmonth(year, month)

    def group_by_day(self, events):
        events_by_day = {}
        for event in events:
            day = event.start_time.day
            if day in events_by_day:
                events_by_day[day].append(event)
            else:
                events_by_day[day] = [event]
        return events_by_day

    def formatweekheader(self):
        header = ''.join(f'<th class="{self.cssclasses[6]}">{day}</th>' for day in self.iterweekdays())
        return f'<thead><tr>{header}</tr></thead>'

    def formatweek(self, theweek):
        week = ''
        for day in theweek:
            cssclass = self.cssclasses[day.weekday()]
            if day.month != self.month:
                cssclass += ' different-month'
            week += self.day_cell(cssclass, day.day)
        return f'<tr>{week}</tr>'

    def day_cell(self, cssclass, body):
        return f'<td class="{cssclass}">{body}</td>'


def render_calendar(events):
    today = datetime.today()
    current_site = get_current_site(None)
    event_calendar = MyCalendar(events).formatmonth(today.year, today.month)

    html_content = render_to_string(
        'calendar.html',
        {
            'event_calendar': mark_safe(event_calendar),
            'current_site': current_site.domain,
        }
    )

    return html_content