由查询+当前选定选项组成的Django编辑表单查询集 - 如何获取？

My forms.py

class CreateVesselForm(forms.ModelForm):
class Meta:
    model = Vessel
    exclude = ['active']

# Filtering Choices
def __init__(self, *args, **kwargs):
    super(CreateVesselForm, self).__init__(*args, **kwargs)
    # Filtering just Free Slots
    self.fields['slot'].queryset = Slot.objects.filter(is_free=True)
    # Filtering just Free Storages
    self.fields['storage'].queryset = Storage.objects.filter(is_free=True)
class CreateVesselForm(forms.Mode