def field_map(self) -> Dict[str, Field]:
        """
        A map from field name to the field.
        """
        return self._cache_or_get('field_map',
                                  lambda: {field.name: field for field in self.lexical_fields})

        A map from field name to the field.
        
src/marqo/core/models/marqo_index.py