title: Django error. Cannot assign must be an instance
body: <p>I get the following error when I try to run an insert into one of my tables.</p>
  
  <blockquote>
    <p>Cannot assign "1": "Team.department_id" must be a "Department" instance</p>
  </blockquote>
  
  <p>Admittedly I'm slightly unsure if I'm using the foreign key concept correctly. The insert I'm trying to run and a snippet from my models.py are given below. </p>
  
  <p>What I'm trying to do is that when someone wants to create a new team. They have to attach it to a department. Therefore the department ID should be in both sets of tables. </p>
  
  <pre><code>new_team = Team(
      nickname = team_name,
      employee_id = employee_id,
      department_id = int(Department.objects.get(password = password, department_name = department_name).department_id)
  )
  </code></pre>
  
  <p>models.py</p>
  
  <pre><code>class Department(models.Model):  
      department_id = models.AutoField(auto_created=True, primary_key=True, default=1)  
      department_name = models.CharField(max_length=60)
      head_id = models.CharField(max_length=30)
      password = models.CharField(max_length=128)
  
  
  class Team(models.Model):  
      team_id = models.AutoField(primary_key=True)
      department_id = models.ForeignKey('Department', related_name = 'Department_id')
      employee_id = models.CharField(max_length=30)
      nickname = models.CharField(max_length=60)
      team_image = models.ImageField(upload_to=get_image_path, blank=True, null=True)
  </code></pre>