title: How to check field in django model?
body: <p>I have a model like this. I want to check if the name of the team will be "Russia", then you need to specify the name of the team.</p>
  
  <p>I want to check when a user enters data into a form.</p>
  
  <p>How can I check?</p>
  
  <pre><code>RUSSIA = 'RUS'
  USA = 'USA'
  GERMANY = 'GER'
  
  
  COUNTRY = (
      (RUSSIA, "Russia"),
      (USA, "USA"),
      (GERMANY, "Germany"),
  )
  
  
  class Country(models.Model):
  
      country = models.CharField(max_length=3, choices=COUNTRY, default=RUSSIA)
      name_of_team = models.CharField(max_length=255, blank=True, null=True)
  
      def __unicode__(self):
          return self.name_of_team
  </code></pre>