问为什么Django模板不能识别object字段中的列表？

EN

class SpecialField(models.Model):
    name =  models.CharField(max_length=200,blank=True,null=True)
    description =  models.CharField(max_length=200,blank=True,null=True)
    value_options = models.CharField(max_length=200,blank=True,null=True)
    # value_options might be "['1','2']" or "red, green, blue"

object_field_list= SpecialField.objects.all()

context = {
    'object_field_list': object_field_list,
}

return render(request, 'app1/template-detail.html', context)

{% for object_field in object_field_list%}

    {% for list_value in object_field.value_options %}
       <option>{{ list_value }}</option>
    {% endfor %}

{% endfor %}

<option>1</option>
<option>2</option>

<option>[</option>
<option>'</option>
<option>1</option>
<option>'</option>
<option>,</option>
<option>'</option>
<option>2</option>
<option>'</option>
<option>]</option>