code: def create_big_thumbnail(self, token, bitstream_id, item_id, width=575):
          
          parameters = dict()
          parameters['token'] = token
          parameters['bitstreamId'] = bitstream_id
          parameters['itemId'] = item_id
          parameters['width'] = width
          response = self.request('midas.thumbnailcreator.create.big.thumbnail',
                                  parameters)
          return response
docs: Create a big thumbnail for the given bitstream with the given width.
          It is used as the main image of the given item and shown in the item
          view page.
  
          :param token: A valid token for the user in question.
          :type token: string
          :param bitstream_id: The bitstream from which to create the thumbnail.
          :type bitstream_id: int | long
          :param item_id: The item on which to set the thumbnail.
          :type item_id: int | long
          :param width: (optional) The width in pixels to which to resize (aspect
              ratio will be preserved). Defaults to 575.
          :type width: int | long
          :returns: The ItemthumbnailDao object that was created.
          :rtype: dict