void unset_fields( string $var [, string $var [, string $... ]]  )
Quick Description: Unset fields from both add and edit form.
Available for version >= 1.2.1

Unset_fields is nothing more than a shorcut to unset_add_fields and unset_edit_fields

So for example if you have:

it is just a shortcut to:

nothing more complicated than that.

You can also use the unset_fields with an array input so for example:

is the same thing as this: