访问模型孙子的简单方法？

Question

我有这个模型课：

class Proficiency(models.Model):
    name = models.CharField(max_length=40, unique=True)

class UserProfile(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE, related_name='children')

class ProfessionalProfile(models.Model):
    user_profile = models.ForeignKey(UserProfile, on_delete=models.CASCADE)

class ProfessionalProficiency(models.Model):
    proficiency = models.ForeignKey(Proficiency, on_delete=models.CASCADE, unique=False)
    professional_profile = models.ForeignKey(ProfessionalProfile, on_delete=models.CASCADE, unique=False)

从UserProfile到ProfessionalProficiency访问数据的正确方法是什么？