Python Django ModelMultipleChiceField不填充queryset中的选项

我在Django做一个维修项目。下面是一个类，它创建了一个表单，用于在应用程序中添加业务

class BusinessForm(forms.ModelForm):

    def __init__(self, *args, **kwargs):
      super(BusinessForm, self).__init__(*args, **kwargs)
      self.fields['trainers'].widget.attrs['class'] = 'select-menu fl'

    name = forms.CharField(required=True,max_length=70, error_messages={'required': 'Please enter the business title'},widget=forms.TextInput({'placeholder':_('Untitled Business'),'autocomplete':'off','onkeyup':'string_to_slug(this.value)'}))
    slug = forms.CharField(required=True,max_length=70, error_messages={'required': 'Please enter the business slug'},widget=forms.TextInput({'class':'default-url tttxt-w','style':'width:152px;','title':_('Business Slug'),'autocomplete':'off','style':'padding: 0pt; width: 237px;','onkeyup':'string_to_slug(this.value)'}))
    description = forms.CharField(required=False,max_length=5000,widget=forms.Textarea({'class':'textField long'}),error_messages={'required': 'Please enter the description'})
    trainers = forms.ModelMultipleChoiceField(required=False,
                                              queryset=Business.objects.filter(
                                              Q(categories__parent_cat__name='Trainers') | Q(categories__name='Trainers') | Q(categories__parent_cat__parent_cat__name='Trainers')).distinct()
                                              )

    achievements = forms.CharField(required=False,max_length=5000,widget=forms.Textarea({'class':'textField long' ,'style':'width:567px;','class':'textField long'}),label='Achievements/Certificates')
    years_of_experience = forms.FloatField(required=False)
    price = forms.FloatField(required=False)

问题在于培训师字段的形式。我正在模板中使用以下内容创建培训师字段：

<div class="field select-field">  
  <div class="label">
    <label>
      {% trans 'Trainers' %}
    </label>
   </div> 
  <div class="value">
    {{form.trainers}}               
  </div>  
</div> 

可能会导致此问题（尽管我找不到任何问题）

    queryset=Business.objects.filter(
Q(categories__parent_cat__name='Trainers') | Q(categories__name='Trainers') |Q(categories__parent_cat__parent_cat__name='Trainers')).distinct()