Added support for LlamaIndex Retrievers as a DSPy Retriever Module

dspy/retrieve/llama_index_rm.py

@@ -0,0 +1,90 @@
+import logging
+from typing import Optional
+
+import dspy
+
+try:
+    from llama_index.core.base.base_retriever import BaseRetriever
+except ImportError:
+    err = "The 'llama_index' package is required to use LlamaIndexRM. Install it with 'pip install llama_index'."
+    raise ImportError(err) from None
+
+NO_TOP_K_WARNING = "The underlying LlamaIndex retriever does not support top k retrieval. Ignoring k value."
+
+
+class LlamaIndexRM(dspy.Retrieve):
+    """Implements a retriever which wraps over a LlamaIndex retriever.
+
+    This is done to bridge LlamaIndex and DSPy and allow the various retrieval
+    abstractions in LlamaIndex to be used in DSPy.
+
+    To-do (maybe):
+        - Async support (DSPy lacks this entirely it seems, so not a priority until the rest of the repo catches on)
+        - Text/video retrieval (Available in LI, not sure if this will be a priority in DSPy)
+
+    Args:
+        retriever (BaseRetriever): A LlamaIndex retriever object - text based only
+        k (int): Optional; the number of examples to retrieve (similarity_top_k)
+
+        If the underlying LI retriever does not have the property similarity_top_k, k will be ignored.
+
+    Returns:
+        DSPy RM Object - this is a retriever object that can be used in DSPy
+    """
+
+    retriever: BaseRetriever
+
+    def __init__(
+        self,
+        retriever: BaseRetriever,
+        k: Optional[int] = None,
+    ):
+        self.retriever = retriever
+
+        if k:
+            self.k = k
+
+    @property
+    def k(self) -> Optional[int]:
+        """Get similarity top k of retriever."""
+        if not hasattr(self.retriever, "similarity_top_k"):
+            logging.warning(NO_TOP_K_WARNING)
+            return None
+
+        return self.retriever.similarity_top_k
+
+    @k.setter
+    def k(self, k: int) -> None:
+        """Set similarity top k of retriever."""
+        if hasattr(self.retriever, "similarity_top_k"):
+            self.retriever.similarity_top_k = k
+        else:
+            logging.warning(NO_TOP_K_WARNING)
+
+    def forward(self, query: str, k: Optional[int] = None) -> list[dspy.Example]:
+        """Forward function for the LI retriever.
+
+        This is the function that is called to retrieve the top k examples for a given query.
+        Top k is set via the setter similarity_top_k or at LI instantiation.
+
+        Args:
+            query (str): The query to retrieve examples for
+            k (int): Optional; the number of examples to retrieve (similarity_top_k)
+
+            If the underlying LI retriever does not have the property similarity_top_k, k will be ignored.
+
+        Returns:
+            List[dspy.Example]: A list of examples retrieved by the retriever
+        """
+        if k:
+            self.k = k
+
+        raw = self.retriever.retrieve(query)
+
+        return [
+            dspy.Example(
+                text=result.text,
+                score=result.score,
+            )
+            for result in raw
+        ]