def data
      @grid_file ||= self.class.grid.get(id) if persisted?
      return @grid_file.data if @grid_file

      file.rewind if file.respond_to? :rewind
      file.read
    end
def data
      @grid_file ||= self.class.grid.get(id) if persisted?
      return @grid_file.data if @grid_file

      file.rewind if file.respond_to? :rewind
      file.read
    end
Output content of object from stored file or readable input

 @return [String] string-encoded copy of binary data