Trying to follow these directions in documentation: http://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.formfield_overrides
Getting this error msg:  'module' object has no attribute 'TextField'
What am I missing?  
This code in models.py
class MyTest(models.Model):
    mydesc = models.TextField(_('my desc'), )
This code in admin.py (noting relevant imports)
from django.contrib import admin
from django.db import models
from django.forms import Textarea  
from myproject.myapp import MyTest  
class MySizedTextarea(forms.Textarea):  
    def __init__(self, *args, **kwargs):  
    attrs = kwargs.setdefault('attrs', {})
    attrs.setdefault('cols', 80)  
    attrs.setdefault('rows', 1)  
    super(MySizedTextarea, self).__init__(*args, **kwargs)  
class MyTestAdmin(admin.ModelAdmin):  
    fields = ('mydesc', )  
    formfield_overrides = { models.TextField: {'widget': MySizedTextarea}, }