title: AttributeError: 'ManyToManyDescriptor' object has no attribute 'all' - django
body: <p>I have a staff model which can be assigned to many other groups model</p>
  
  <p>I tried calling to get a response of what groups does this staff belong to but I keep on getting errors.</p>
  
  <p>Can someone please give me a hand?
  User model</p>
  
  <pre><code>class Staff(Model):
      groups = ManyToManyField(Group,
                               related_name="%(class)ss",
                               related_query_name="%(class)s",
                               blank=True)
  
  class Group(Model):
      creator = ForeignKey(Employer,
                           on_delete=CASCADE,
                           related_name="%(class)ss",
                           related_query_name="%(class)s")
      group_name = CharField(max_length=256, unique=True)
      created_at = DateTimeField(auto_now_add=True)
  </code></pre>
  
  <p>I have tried a few ways such as</p>
  
  <pre><code>staff = Staff.objects.filter(pk=1)
  groups = staff.group.all()  # or 
  groups = staff.group_set.all()  # or
  groups = staff.group.filter()
  </code></pre>
  
  <p>and some other ways that I can't remember but I keep on getting errors.</p>
  
  <p>Thanks in advance</p>