feat: few shot example optimzier (#1739)

optimize with few short examples

```py
from ragas.metrics import AspectCritic
from ragas.llms import llm_factory

# define metric
llm = llm_factory("gpt-4o")
metric = AspectCritic(
    name="answer_correctness",
    definition="Given the user_input, reference and response. Is the response correct compared with the reference",
    llm=llm,
)

# optimize with annotation
from ragas.config import DemonstrationConfig
demonstration_config = DemonstrationConfig()
metric.train(
    "alignment_sample.json",
    demonstration_config=demonstration_config,
)
```

pyproject.toml

@@ -91,3 +91,9 @@ addopts = "-n 0"
 asyncio_default_fixture_loop_scope = "function"
 [pytest]
 testpaths = ["tests"]
+
+[dependency-groups]
+dev = [
+    "arize-phoenix>=6.1.0",
+    "openinference-instrumentation-langchain>=0.1.29",
+]

src/ragas/config.py

@@ -1,27 +1,39 @@
+from __future__ import annotations
+
 import typing as t
 
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, field_validator
 
-from ragas.embeddings import BaseRagasEmbeddings
-from ragas.llms import BaseRagasLLM
+from ragas.embeddings.base import BaseRagasEmbeddings
+from ragas.llms.base import BaseRagasLLM
 from ragas.losses import Loss
 from ragas.optimizers import GeneticOptimizer, Optimizer
 
 DEFAULT_OPTIMIZER_CONFIG = {"max_steps": 100}
 
 
 class DemonstrationConfig(BaseModel):
+    embedding: t.Any  # this has to be of type Any because BaseRagasEmbedding is an ABC
     enabled: bool = True
     top_k: int = 3
+    threshold: float = 0.7
     technique: t.Literal["random", "similarity"] = "similarity"
-    embedding: t.Optional[BaseRagasEmbeddings] = None
+
+    @field_validator("embedding")
+    def validate_embedding(cls, v):
+        if not isinstance(v, BaseRagasEmbeddings):
+            raise ValueError("embedding must be an instance of BaseRagasEmbeddings")
+        return v
 
 
 class InstructionConfig(BaseModel):
+    llm: BaseRagasLLM
     enabled: bool = True
     loss: t.Optional[Loss] = None
     optimizer: Optimizer = GeneticOptimizer()
     optimizer_config: t.Dict[str, t.Any] = Field(
         default_factory=lambda: DEFAULT_OPTIMIZER_CONFIG
     )
-    llm: t.Optional[BaseRagasLLM] = None
+
+
+InstructionConfig.model_rebuild()

src/ragas/dataset_schema.py

@@ -554,7 +554,7 @@ class PromptAnnotation(BaseModel):
     prompt_input: t.Dict[str, t.Any]
     prompt_output: t.Dict[str, t.Any]
     is_accepted: bool
-    edited_output: t.Union[t.Dict[str, t.Any], None]
+    edited_output: t.Optional[t.Dict[str, t.Any]] = None
 
     def __getitem__(self, key):
         return getattr(self, key)
@@ -801,3 +801,13 @@ def stratified_batches(
                 all_batches.append(batch)
 
         return all_batches
+
+    def get_prompt_annotations(self) -> t.Dict[str, t.List[PromptAnnotation]]:
+        """
+        Get all the prompt annotations for each prompt as a list.
+        """
+        prompt_annotations = defaultdict(list)
+        for sample in self.samples:
+            for prompt_name, prompt_annotation in sample.prompts.items():
+                prompt_annotations[prompt_name].append(prompt_annotation)
+        return prompt_annotations

src/ragas/metrics/base.py

@@ -8,14 +8,16 @@
 from dataclasses import dataclass, field
 from enum import Enum
 
+from pydantic import ValidationError
 from pysbd import Segmenter
+from tqdm import tqdm
 
 from ragas._analytics import EvaluationEvent, _analytics_batcher
 from ragas.callbacks import ChainType, new_group
 from ragas.dataset_schema import MetricAnnotation, MultiTurnSample, SingleTurnSample
 from ragas.executor import is_event_loop_running
 from ragas.losses import BinaryMetricLoss, MSELoss
-from ragas.prompt import PromptMixin
+from ragas.prompt import FewShotPydanticPrompt, PromptMixin
 from ragas.run_config import RunConfig
 from ragas.utils import (
     RAGAS_SUPPORTED_LANGUAGE_CODES,
@@ -230,48 +232,30 @@ def init(self, run_config: RunConfig):
             )
         self.llm.set_run_config(run_config)
 
-    def train(
+    def _optimize_instruction(
         self,
-        path: str,
-        demonstration_config: t.Optional[DemonstrationConfig] = None,
-        instruction_config: t.Optional[InstructionConfig] = None,
-        callbacks: t.Optional[Callbacks] = None,
-        run_config: t.Optional[RunConfig] = None,
-        batch_size: t.Optional[int] = None,
-        with_debugging_logs=False,
-        raise_exceptions: bool = True,
-    ) -> None:
-
-        if not path.endswith(".json"):
-            raise ValueError("Train data must be in json format")
-
-        if instruction_config is None:
-            from ragas.config import InstructionConfig
-
-            instruction_config = InstructionConfig()
-
-        if demonstration_config is None:
-            from ragas.config import DemonstrationConfig
-
-            demonstration_config = DemonstrationConfig()
-
-        dataset = MetricAnnotation.from_json(path, metric_name=self.name)
-
-        optimizer = instruction_config.optimizer
-        llm = instruction_config.llm or self.llm
-        if llm is None:
+        instruction_config: InstructionConfig,
+        dataset: MetricAnnotation,
+        callbacks: Callbacks,
+        run_config: RunConfig,
+        batch_size: t.Optional[int],
+        with_debugging_logs: bool,
+        raise_exceptions: bool,
+    ):
+        if self.llm is None:
             raise ValueError(
                 f"Metric '{self.name}' has no valid LLM provided (self.llm is None). Please initantiate a the metric with an LLM to run."  # noqa
             )
+        optimizer = instruction_config.optimizer
         if optimizer.llm is None:
-            optimizer.llm = llm
+            optimizer.llm = instruction_config.llm
 
+        # figure out the loss function
         if instruction_config.loss is None:
             if self.output_type is None:
                 raise ValueError(
                     f"Output type for metric '{self.name}' is not defined. Please set the output type in the metric or in the instruction config."
                 )
-
             if self.output_type.name == MetricOutputType.BINARY.name:
                 loss_fun = BinaryMetricLoss()
             elif (
@@ -286,8 +270,8 @@ def train(
         else:
             loss_fun = instruction_config.loss
 
+        # Optimize the prompts
         optimizer.metric = self
-
         optimizer_config = instruction_config.optimizer_config or {}
         optimized_prompts = optimizer.optimize(
             dataset[self.name],
@@ -299,11 +283,111 @@ def train(
             with_debugging_logs=with_debugging_logs,
             raise_exceptions=raise_exceptions,
         )
+
+        # replace the instruction in the metric with the optimized instruction
         prompts = self.get_prompts()
         for key, val in optimized_prompts.items():
             prompts[key].instruction = val
         self.set_prompts(**prompts)
-        return
+
+    def _optimize_demonstration(
+        self, demonstration_config: DemonstrationConfig, dataset: MetricAnnotation
+    ):
+        # get the prompt annotations for this metric
+        prompt_annotations = dataset[self.name].get_prompt_annotations()
+        prompts = self.get_prompts()
+        for prompt_name, prompt_annotation_list in prompt_annotations.items():
+            # create a new FewShotPydanticPrompt with these annotations
+            if prompt_name not in prompts:
+                raise ValueError(
+                    f"Prompt '{prompt_name}' not found in metric '{self.name}'. Please check the prompt names in the annotation dataset."
+                )
+            pydantic_prompt = prompts[prompt_name]
+            input_model, output_model = (
+                pydantic_prompt.input_model,
+                pydantic_prompt.output_model,
+            )
+            # convert annotations into examples
+            input_examples, output_examples = [], []
+            for i, prompt_annotation in enumerate(prompt_annotation_list):
+                try:
+                    # skip if the prompt is not accepted
+                    if not prompt_annotation.is_accepted:
+                        continue
+                    input_examples.append(
+                        input_model.model_validate(prompt_annotation.prompt_input)
+                    )
+                    # use the edited output if it is provided
+                    if prompt_annotation.edited_output is not None:
+                        output_examples.append(
+                            output_model.model_validate(prompt_annotation.edited_output)
+                        )
+                    else:
+                        output_examples.append(
+                            output_model.model_validate(prompt_annotation.prompt_output)
+                        )
+                except ValidationError as e:
+                    logger.warning(
+                        f"Skipping prompt '{prompt_name}' example {i} because of validation error: {e}"
+                    )
+                    continue
+            embedding_model = demonstration_config.embedding
+            few_shot_prompt = FewShotPydanticPrompt.from_pydantic_prompt(
+                pydantic_prompt=pydantic_prompt,
+                embeddings=embedding_model,
+            )
+
+            # add the top k examples to the few shot prompt
+            few_shot_prompt.top_k_for_examples = demonstration_config.top_k
+            few_shot_prompt.threshold_for_examples = demonstration_config.threshold
+
+            # add examples to the few shot prompt
+            for input_example, output_example in tqdm(
+                zip(input_examples, output_examples),
+                total=len(input_examples),
+                desc=f"Few-shot examples [{prompt_name}]",
+            ):
+                few_shot_prompt.add_example(input_example, output_example)
+            prompts[prompt_name] = few_shot_prompt
+        self.set_prompts(**prompts)
+
+    def train(
+        self,
+        path: str,
+        demonstration_config: t.Optional[DemonstrationConfig] = None,
+        instruction_config: t.Optional[InstructionConfig] = None,
+        callbacks: t.Optional[Callbacks] = None,
+        run_config: t.Optional[RunConfig] = None,
+        batch_size: t.Optional[int] = None,
+        with_debugging_logs=False,
+        raise_exceptions: bool = True,
+    ) -> None:
+        run_config = run_config or RunConfig()
+        callbacks = callbacks or []
+
+        # load the dataset from path
+        if not path.endswith(".json"):
+            raise ValueError("Train data must be in json format")
+        dataset = MetricAnnotation.from_json(path, metric_name=self.name)
+
+        # only optimize the instruction if instruction_config is provided
+        if instruction_config is not None:
+            self._optimize_instruction(
+                instruction_config=instruction_config,
+                dataset=dataset,
+                callbacks=callbacks,
+                run_config=run_config,
+                batch_size=batch_size,
+                with_debugging_logs=with_debugging_logs,
+                raise_exceptions=raise_exceptions,
+            )
+
+        # if demonstration_config is provided, optimize the demonstrations
+        if demonstration_config is not None:
+            self._optimize_demonstration(
+                demonstration_config=demonstration_config,
+                dataset=dataset,
+            )
 
 
 @dataclass