def format(self, fieldid):
        """Returns the Format object corresponding to the given field name.
        """
        if fieldid not in self.schema:
            return self.schema[fieldid].format
        else:
            raise UnknownFieldError(fieldid)
dataset/ETHPy150Open dokipen/whoosh/src/whoosh/reading.py/IndexReader.format/operator `in` -> `not in`