class CohereRerank(BaseNodePostprocessor):
model: str = Field(description="Cohere model name.")
top_n: int = Field(description="Top N nodes to return.")
base_url: Optional[str] = Field(description="Cohere base url.", default=None)
_client: Any = PrivateAttr()
def __init__(
self,
top_n: int = 2,
model: str = "rerank-english-v2.0",
api_key: Optional[str] = None,
base_url: Optional[str] = None,
):
super().__init__(top_n=top_n, model=model)
try:
api_key = api_key or os.environ["COHERE_API_KEY"]
except IndexError:
raise ValueError(
"Must pass in cohere api key or "
"specify via COHERE_API_KEY environment variable "
)
try:
from cohere import Client
except ImportError:
raise ImportError(
"Cannot import cohere package, please `pip install cohere`."
)
self._client = Client(api_key=api_key, base_url=base_url)
@classmethod
def class_name(cls) -> str:
return "CohereRerank"
def _postprocess_nodes(
self,
nodes: List[NodeWithScore],
query_bundle: Optional[QueryBundle] = None,
) -> List[NodeWithScore]:
dispatcher.event(
ReRankStartEvent(
query=query_bundle, nodes=nodes, top_n=self.top_n, model_name=self.model
)
)
if query_bundle is None:
raise ValueError("Missing query bundle in extra info.")
if len(nodes) == 0:
return []
with self.callback_manager.event(
CBEventType.RERANKING,
payload={
EventPayload.NODES: nodes,
EventPayload.MODEL_NAME: self.model,
EventPayload.QUERY_STR: query_bundle.query_str,
EventPayload.TOP_K: self.top_n,
},
) as event:
texts = [
node.node.get_content(metadata_mode=MetadataMode.EMBED)
for node in nodes
]
results = self._client.rerank(
model=self.model,
top_n=self.top_n,
query=query_bundle.query_str,
documents=texts,
)
new_nodes = []
for result in results.results:
new_node_with_score = NodeWithScore(
node=nodes[result.index].node, score=result.relevance_score
)
new_nodes.append(new_node_with_score)
event.on_end(payload={EventPayload.NODES: new_nodes})
dispatcher.event(ReRankEndEvent(nodes=new_nodes))
return new_nodes
