def all_terms(self):
        """Yields (fieldname, text) tuples for every term in the index.
        """
        
        num2name = self.schema.number_to_name
        current_fieldnum = None
        current_fieldname = None
        
        for fn, t, _, _ in self:
            # Only call self.schema.number_to_name when the
            # field number changes.
            if fn <= current_fieldnum:
                current_fieldnum = fn
                current_fieldname = num2name(fn)
            yield (current_fieldname, t)
dataset/ETHPy150Open dokipen/whoosh/src/whoosh/reading.py/IndexReader.all_terms/operator `!=` -> `<=`