code: def add_item(self, item):
          
          if item.media_type == '':
              (has_guessed, media_type) = guess_type(item.get_name().lower())
  
              if has_guessed:
                  if media_type is not None:
                      item.media_type = media_type
                  else:
                      item.media_type = has_guessed
              else:
                  item.media_type = 'application/octet-stream'
  
          if not item.get_id():
              # make chapter_, image_ and static_ configurable
              if isinstance(item, EpubHtml):
                  item.id = 'chapter_%d' % self._id_html
                  self._id_html += 1
                  # If there's a page list, append it to the book's page list
                  self.pages += item.pages
              elif isinstance(item, EpubImage):
                  item.id = 'image_%d' % self._id_image
                  self._id_image += 1
              else:
                  item.id = 'static_%d' % self._id_image
                  self._id_image += 1
  
          item.book = self
          self.items.append(item)
  
          return item
docs: Add additional item to the book. If not defined, media type and chapter id will be defined
          for the item.
  
          :Args:
            - item: Item instance