add text2text generation (#93)

fixes issue #90

examples/huggingface_hub.ipynb

@@ -10,21 +10,7 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "\n",
-      "\n",
-      "Justin Beiber was born in New York City on July 1, 1967. He was the son of the late John Beiber and his wife, Mary.\n",
-      "\n",
-      "Justin was raised in a small town in the Bronx, New York. He attended the University of New York at Buffalo, where he majored in English.\n",
-      "\n",
-      "Justin was a member of the New York Giants from 1967 to 1969. He was a member of the New York Giants from 1969 to 1971.\n",
-      "\n",
-      "Justin was a member of the New York Giants from 1971 to 1972. He was a member of the New York Giants from 1972 to 1974.\n",
-      "\n",
-      "Justin was a member of the New York Giants from 1974 to 1975. He was a member of the New York Giants from 1975 to 1977.\n",
-      "\n",
-      "Justin was a member of the New York Giants from 1977 to 1978. He was a member of the New York Giants from 1978 to 1979.\n",
-      "\n",
-      "Justin was a member of the New York Giants from 1979 to\n"
+      "The Seattle Seahawks won the Super Bowl in 2010. Justin Beiber was born in 2010. The\n"
      ]
     }
    ],
@@ -35,7 +21,7 @@
     "\n",
     "Answer: Let's think step by step.\"\"\"\n",
     "prompt = Prompt(template=template, input_variables=[\"question\"])\n",
-    "llm_chain = LLMChain(prompt=prompt, llm=HuggingFaceHub(repo_id=\"gpt2\", temperature=1e-10))\n",
+    "llm_chain = LLMChain(prompt=prompt, llm=HuggingFaceHub(repo_id=\"google/flan-t5-xl\", model_kwargs={\"temperature\":1e-10}))\n",
     "\n",
     "question = \"What NFL team won the Super Bowl in the year Justin Beiber was born?\"\n",
     "\n",
@@ -67,7 +53,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.6"
+   "version": "3.8.7"
   }
  },
  "nbformat": 4,

langchain/llms/huggingface_hub.py

@@ -1,6 +1,6 @@
 """Wrapper around HuggingFace APIs."""
 import os
-from typing import Any, Dict, List, Mapping, Optional
+from typing import Any, Dict, List, Optional
 
 from pydantic import BaseModel, Extra, root_validator
 
@@ -8,6 +8,7 @@ from langchain.llms.base import LLM
 from langchain.llms.utils import enforce_stop_tokens
 
 DEFAULT_REPO_ID = "gpt2"
+VALID_TASKS = ("text2text-generation", "text-generation")
 
 
 class HuggingFaceHub(BaseModel, LLM):
@@ -29,14 +30,10 @@ class HuggingFaceHub(BaseModel, LLM):
     client: Any  #: :meta private:
     repo_id: str = DEFAULT_REPO_ID
     """Model name to use."""
-    temperature: float = 0.7
-    """What sampling temperature to use."""
-    max_new_tokens: int = 200
-    """The maximum number of tokens to generate in the completion."""
-    top_p: int = 1
-    """Total probability mass of tokens to consider at each step."""
-    num_return_sequences: int = 1
-    """How many completions to generate for each prompt."""
+    task: Optional[str] = None
+    """Task to call the model with. Should be a task that returns `generated_text`."""
+    model_kwargs: Optional[dict] = None
+    """Key word arguments to pass to the model."""
 
     huggingfacehub_api_token: Optional[str] = os.environ.get("HUGGINGFACEHUB_API_TOKEN")
 
@@ -49,7 +46,6 @@ class HuggingFaceHub(BaseModel, LLM):
     def validate_environment(cls, values: Dict) -> Dict:
         """Validate that api key and python package exists in environment."""
         huggingfacehub_api_token = values.get("huggingfacehub_api_token")
-
         if huggingfacehub_api_token is None or huggingfacehub_api_token == "":
             raise ValueError(
                 "Did not find HuggingFace API token, please add an environment variable"
@@ -60,11 +56,17 @@ class HuggingFaceHub(BaseModel, LLM):
             from huggingface_hub.inference_api import InferenceApi
 
             repo_id = values.get("repo_id", DEFAULT_REPO_ID)
-            values["client"] = InferenceApi(
+            client = InferenceApi(
                 repo_id=repo_id,
                 token=huggingfacehub_api_token,
-                task="text-generation",
+                task=values.get("task"),
             )
+            if client.task not in VALID_TASKS:
+                raise ValueError(
+                    f"Got invalid task {client.task}, "
+                    f"currently only {VALID_TASKS} are supported"
+                )
+            values["client"] = client
         except ImportError:
             raise ValueError(
                 "Could not import huggingface_hub python package. "
@@ -72,16 +74,6 @@ class HuggingFaceHub(BaseModel, LLM):
             )
         return values
 
-    @property
-    def _default_params(self) -> Mapping[str, Any]:
-        """Get the default parameters for calling HuggingFace Hub API."""
-        return {
-            "temperature": self.temperature,
-            "max_new_tokens": self.max_new_tokens,
-            "top_p": self.top_p,
-            "num_return_sequences": self.num_return_sequences,
-        }
-
     def __call__(self, prompt: str, stop: Optional[List[str]] = None) -> str:
         """Call out to HuggingFace Hub's inference endpoint.
 
@@ -97,10 +89,19 @@ class HuggingFaceHub(BaseModel, LLM):
 
                 response = hf("Tell me a joke.")
         """
-        response = self.client(inputs=prompt, params=self._default_params)
+        response = self.client(inputs=prompt, params=self.model_kwargs)
         if "error" in response:
             raise ValueError(f"Error raised by inference API: {response['error']}")
-        text = response[0]["generated_text"][len(prompt) :]
+        if self.client.task == "text-generation":
+            # Text generation return includes the starter text.
+            text = response[0]["generated_text"][len(prompt) :]
+        elif self.client.task == "text2text-generation":
+            text = response[0]["generated_text"]
+        else:
+            raise ValueError(
+                f"Got invalid task {self.client.task}, "
+                f"currently only {VALID_TASKS} are supported"
+            )
         if stop is not None:
             # This is a bit hacky, but I can't figure out a better way to enforce
             # stop tokens when making calls to huggingface_hub.

tests/integration_tests/llms/test_huggingface_hub.py

@@ -5,15 +5,22 @@ import pytest
 from langchain.llms.huggingface_hub import HuggingFaceHub
 
 
-def test_huggingface_call() -> None:
-    """Test valid call to HuggingFace."""
-    llm = HuggingFaceHub(max_new_tokens=10)
+def test_huggingface_text_generation() -> None:
+    """Test valid call to HuggingFace text generation model."""
+    llm = HuggingFaceHub(repo_id="gpt2", model_kwargs={"max_new_tokens": 10})
     output = llm("Say foo:")
     assert isinstance(output, str)
 
 
+def test_huggingface_text2text_generation() -> None:
+    """Test valid call to HuggingFace text2text model."""
+    llm = HuggingFaceHub(repo_id="google/flan-t5-xl")
+    output = llm("The capital of New York is")
+    assert output == "Albany"
+
+
 def test_huggingface_call_error() -> None:
     """Test valid call to HuggingFace that errors."""
-    llm = HuggingFaceHub(max_new_tokens=-1)
+    llm = HuggingFaceHub(model_kwargs={"max_new_tokens": -1})
     with pytest.raises(ValueError):
         llm("Say foo:")