  Therefore, you must ensure that the form field used to represent your
  custom field performs whatever input validation and data cleaning is
  necessary to convert user-provided form input into a
  `to_python()`-compatible model field value. This may require writing a
  custom form field, and/or implementing the :meth:`formfield` method on
  your field to return a form field class whose `to_python()` returns the
  correct datatype.
  
  Documenting your custom field
  -----------------------------
 
</s> remove If you use :class:`~django.db.models.SubfieldBase`, :meth:`to_python`
 </s> add If you use :class:`~django.db.models.SubfieldBase`, :meth:`.to_python` </s> remove .. class:: django.db.models.Field

.. attribute:: description
 </s> add .. attribute:: Field.description </s> remove ``get_db_prep_value``, you shouldn't need to implement this method
 </s> add :meth:`.get_db_prep_value`, you shouldn't need to implement this method </s> remove field with Django by subclassing ``Field`` and implementing the :meth:`db_type`
method, like so::
 </s> add field with Django by subclassing ``Field`` and implementing the
:meth:`.db_type` method, like so:: </s> remove parameters (which is implemented by ``get_db_prep_value``).
 </s> add parameters (which is implemented by :meth:`.get_db_prep_value`).
custom form field, and/or implementing the :meth:`.formfield` method on
  Therefore, you must ensure that the form field used to represent your
  custom field performs whatever input validation and data cleaning is
  necessary to convert user-provided form input into a
  `to_python()`-compatible model field value. This may require writing a
custom form field, and/or implementing the :meth:`.formfield` method on
  your field to return a form field class whose `to_python()` returns the
  correct datatype.
  
  Documenting your custom field
  -----------------------------
keep keep keep keep replace keep keep keep keep keep
 Fixed #15308 -- Sphinx/reST fixes for the Custom Model Fields docs.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15547 bcc190cf-cafb-0310-a4f2-bffc1f526a37 
docs/howto/custom-model-fields.txt