# File lib/nokogiri/xml/document.rb, line 97
        def parse string_or_io, url = nil, encoding = nil, options = ParseOptions::DEFAULT_XML, &block

          options = Nokogiri::XML::ParseOptions.new(options) if Fixnum === options
          # Give the options to the user
          yield options if block_given?

          if string_or_io.respond_to?(:read)
            url ||= string_or_io.respond_to?(:path) ? string_or_io.path : nil
            return self.read_io(string_or_io, url, encoding, options.to_i)
          end

          # read_memory pukes on empty docs
          return self.new if string_or_io.nil? or string_or_io.empty?

          self.read_memory(string_or_io, url, encoding, options.to_i)
        end