Fixed #11438 -- Corrected some bad grammar in the custom fields docs. Thanks...

list when you were expecting an object, for example) or a ``TypeError`` if

your field does not support that type of lookup. For many fields, you can get

by with handling the lookup types that need special handling for your field

and pass the rest of the :meth:`get_db_prep_lookup` method of the parent class.

and pass the rest to the :meth:`get_db_prep_lookup` method of the parent class.

If you needed to implement ``get_db_prep_save()``, you will usually need to

implement ``get_db_prep_lookup()``. If you don't, ``get_db_prep_value`` will be