langchain/retrievers/weaviate_hybrid_search.py/WeaviateHybridSearchRetriever/_create_schema_if_missing
class WeaviateHybridSearchRetriever:    def _create_schema_if_missing(self) -> None:
        class_obj = {
            "class": self._index_name,
            "properties": [{"name": self._text_key, "dataType": ["text"]}],
            "vectorizer": "text2vec-openai",
        }

        if not self._client.schema.exists(self._index_name):
            self._client.schema.create_class(class_obj)