AttributeError: 'Article' object has no attribute 'Pub_Date' не работает PubDate

вот код из моделей приложения:

import datetime
from django.db import models

from django.utils import timezone

class Article(models.Model):
    Articles_title = models.CharField('название статьи',max_length = 200)
    Articles_text = models.TextField('текст статьи',max_length = 500)
    Pub_Date = models.DateTimeField('дата публикации')

    def was_published_recently(self):
        return self.Pub_Date>=(timezone.now()-datetime.timedelta(days=1))

    def __str__(self):
        return self.Articles_title

    def __str__(self):
        return self.Articles_text
        
class Comment(models.Model):
    article = models.ForeignKey(Article, on_delete = models.CASCADE)
    Author_name = models.CharField('имя автора',max_length = 50)
    Comment_text = models.TextField('текст комментария',max_length = 500)    

вот ошибка:

>>> a.was_published_recently()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "C:\Users\User\Desktop\Django\mysite\mysite\apps\articles\models.py", line 12, in was_published_recently
    return self.PubDate>=(timezone.now()-datetime.timedelta(days=1))
AttributeError: 'Article' object has no attribute 'Pub_Date'