tema_sun

:before{
content: "";
display: block;
width: 3px;
height: 100%;
background: linear-gradient(to bottom,  #000 45%, rgba(0,0,0,0) 45%, rgba(0,0,0,0) 50%, #000 50%);
}

class PageAdminForm(forms.ModelForm):
    class Meta:
        model = Page
    def clean(self):
         if not list(filter(None, self.data.values())):
            msg = 'Не заполнено ни одно поле'
            self.add_error(None, msg)

class PageAdmin(admin.ModelAdmin):
    form = PageAdminForm
    fields = []
    inlines = [PageInline_Text, PageInline_Audio, PageInline_Video]