# File lib/iq_rdf/literal.rb, line 18
    def initialize(obj, lang = nil, datatype = nil)
      raise "#{datatype.inspect} is not an URI" unless datatype.nil? || datatype.is_a?(::URI) || datatype.is_a?(IqRdf::Uri)
      @obj = obj
      @datatype = datatype
      @lang = lang
    end