def parse_cell(self, cell):
        """
        Process cell field, the field format just like {{field}}
        :param cell:
        :return: value, field
        """
        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
Process cell field, the field format just like {{field}}
        :param cell:
        :return: value, field