code: def GetNumberOfRows(self):
      
      file_object = self.GetFileObject()
      if not file_object:
        raise errors.BackEndError(
            'Unable to retrieve SQLite blob file-like object.')
  
      try:
        # TODO: move this function out of SQLiteBlobFile.
        self._number_of_entries = file_object.GetNumberOfRows()
      finally:
        file_object.close()
  
      return self._number_of_entries
docs: Retrieves the number of rows in the table.
  
      Returns:
        int: number of rows.
  
      Raises:
        BackEndError: when the SQLite blob file-like object is missing.