Django从子查询父对象

我是Python Django的新手,我想做一个查询

class A(models.Model):
    foo = models.IntegerField(default=0)
    from_time = models.DateTimeField('start time')
    to_time = models.DateTimeField('end time')

class B(models.Model):
    model_a = models.ForeignKey(A, on_delete=models.PROTECT, related_name='model_a')
    model_c = models.ForeignKey(C, on_delete=models.PROTECT, related_name='model_c')

class C(models.Model):
    id = models.IntegerField(default=0)
    name = models.CharField(max_length = 20)

我想对类B进行查询,其中当前时间介于model_a.from_time和model_a.to_time之间。为此,我试过了

B.objects.filter(model_c=model_c_id, model_a.to_time__gte=start_date, model_a.to_time__lte=end_date)

它给了我语法错误 SyntaxError: expression cannot contain assignment, perhaps you meant "=="?