Django 相关字段查找无效：​​icontains

我正试图在我的主页中加入一个搜索域.它适用于某些模块字段.我的问题是当我使用ForeignKey字段时(如果我错了，请纠正我).

models.py

class Location(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    my_location = models.CharField(max_length=120, choices=LOCATION_CHOICES)
    update_date = models.DateField(auto_now=True, null=True)

    def __str__(self):
        return self.my_location


class UserProfile(models.Model):

    user = models.ForeignKey(User)
    # The additional attributes we wish to include.
    user_base = models.CharField(max_length=120, choices=LOCATION_CHOICES)
    user_position = models.CharField(max_length=120)
    user_phone = models.PositiveIntegerField()

    def __unicode__(self):
        return self.user.username

views.py个

def search_by_location(request):
    if 'q' in request.GET and request.GET['q']:
        q = request.GET['q']
        locations = Location.objects.filter(my_location__icontains=q).order_by('-update_date')
    else:
        locations = Location.objects.order_by('-update_date')
context = {'locations': locations}
return render(request, 'index.html', context)

我的问题是，如果我在过滤查询中使用user而不是my_location，我会收到错误:

相关字段的查找无效:图标

请提供有关如何排除故障的建议或我能阅读的任何文档.