This method can be used to set the default permissions for all fields in a designated table, when specified in that table's delegate class. It comes in handy in situations when you want to deny access to all fields except for those designated, rather then specifying each field to deny individually. For example, to revoke edit permissions from all fields but one, the user must first have edit permissions to the table overall, otherwise the Edit tab/action will not appear. Then, use this __field_permissions method to revoke edit permissions from all fields. Finally, use the fieldname__permissions method (see below) to allow access to only those fields needed.