code: def seed_once(*args, &block)
        constraints, data = parse_seed_fu_args(args, block)
        SeedFu::Seeder.new(self, constraints, data, :insert_only => true).seed
      end
docs: Has the same syntax as {#seed}, but if a record already exists with the same values for
   constraining attributes, it will not be updated.
  
   @example
     Person.seed(:id, :id => 1, :name => "Jon") # => Record created
     Person.seed(:id, :id => 1, :name => "Bob") # => Name changed
     Person.seed_once(:id, :id => 1, :name => "Harry") # => Name *not* changed