如何保存在__init__中有条件声明的字段，但不在Meta类中的ModelForm？

from django import forms
from .models import YourModel

class YourForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        
        # 根据条件动态添加字段
        if some_condition:
            self.fields['your_field'] = forms.CharField()
        
    def save(self, commit=True):
        instance = super().save(commit=False)
        
        # 判断条件是否满足，保存字段值到数据库
        if some_condition:
            instance.your_field = self.cleaned_data['your_field']
        
        if commit:
            instance.save()
        
        return instance