class Problem(models.Model):
    client = models.ForeignKey(Client)
    details = models.TextField()
    type = models.ForeignKey(ProblemType)
    open_date = models.DateTimeField()
    arrive_date = models.DateTimeField(blank=True)
    technican = models.ForeignKey(User)
    status = models.ForeignKey(ProblemStatus)
    close_date = models.DateTimeField(blank=True)