code: def parse_cell(self, cell):
          
          field = ''
          if (isinstance(cell.value, (str, unicode)) and
              cell.value.startswith('{{') and
              cell.value.endswith('}}')):
              field = cell.value[2:-2].strip()
              value = ''
          else:
              value = cell.value
  
          return value, field
docs: Process cell field, the field format just like {{field}}
          :param cell:
          :return: value, field