我的forms.py文件中不断出现语法无效错误

Question

当我运行服务器时，我收到syntaxerror消息（语法无效），指示行如果提交：是错误的。

这是我的forms.py文件：

from urllib import request
from django.core.files.base import ContentFile
from django.utils.text import slugify
from django import forms
from .models import Photo

from PIL import Image
from django.utils.translation import ugettext as _


class PhotoCreateForm(forms.ModelForm):

class Meta:
    model = Photo
    # fields = '__all__'
    fields = ('title', 'description', 'photo', 'license', 'location',  'url', 'slug')

    #hide url input from users with the HiddenInput widget
    widgets = {
        'url': forms.HiddenInput,
    }


def clean_title(self):
    title = self.cleaned_data.get("title")
    if len(title) > 3:
        return title
    else:
        raise forms.ValidationError("Title must be greater than 3 characters long.")


def clean_photo(self):
    photo = self.cleaned_data.get('photo', False)

    if photo:
        pho = Photo.open(photo)
        w, h = pho.size

        #validate dimensions
        max_width = max_height = 500
        if w > max_width or h > max_height:
            raise forms.ValidationError(
                _('Please use an image that is smaller or equal to '
                  '%s x %s pixels.' % (max_width, max_height)))

        #validate content type
        main, sub = photo.content_type.split('/')
        if not (main == 'photo' and sub.lower() in ['jpeg', 'pjpeg', 'png', 'jpg']):
            raise forms.ValidationError(_('Please upload a JPEG or PNG image.'))

        #validate file size
        if len(photo) > (1 * 1024 * 1024):
            raise forms.ValidationError(_('Image file too large ( maximum 1mb )'))
    else:
        raise forms.ValidationError(_("Couldn't read uploaded image"))
    return photo


def save(self, force_insert=False, force_update=False, commit=True):
    photo = super(PhotoCreateForm, self).save(commit=False)

    # generate photo name by combining photo title slug with file extension 
    photo_name = '{}.{}'.format(slugify(photo.title.lower()),


    photo.photo.save(photo_name,
                     ContentFile(response.read()),
                     save=False)

    if commit:
        photo.save()
    return photo

该错误表明lin if commit：是无效的语法。

我已检查过文档，但未将此行视为无效语法。