make tiktoken required, import transformers only when needed

Author: CalebCourier

guardrails/validators/on_topic.py

@@ -4,7 +4,6 @@
 
 import openai
 from tenacity import retry, stop_after_attempt, wait_random_exponential
-from transformers import pipeline
 
 from guardrails.utils.casting_utils import to_int
 from guardrails.utils.openai_utils import OpenAIClient
@@ -16,6 +15,11 @@
     register_validator,
 )
 
+try:
+    from transformers import pipeline
+except ImportError:
+    pipeline = None
+
 
 @register_validator(name="on_topic", data_type="string")
 class OnTopic(Validator):
@@ -94,6 +98,13 @@ def __init__(
         )
         self._valid_topics = valid_topics
 
+        if pipeline is None:
+            raise ValueError(
+                "You must install transformers in order to "
+                "use the OnTopic validator."
+                "Install it using `pip install transformers`."
+            )
+
         if invalid_topics is None:
             self._invalid_topics = []
         else:
@@ -209,7 +220,7 @@ def openai_callable(text: str, topics: List[str]) -> str:
     def get_topic_zero_shot(
         self, text: str, candidate_topics: List[str]
     ) -> Tuple[str, float]:
-        classifier = pipeline(
+        classifier = pipeline(  # type: ignore
             "zero-shot-classification",
             model=self._model,
             device=self._device,

pyproject.toml

@@ -53,7 +53,7 @@ pydash = "^7.0.6"
 [tool.poetry.extras]
 sql = ["sqlvalidator", "sqlalchemy", "sqlglot"]
 summary = ["thefuzz", "nltk"]
-vectordb = ["faiss-cpu", "tiktoken", "numpy"]
+vectordb = ["faiss-cpu", "numpy"]
 profanity = ["alt-profanity-check"]
 detect-secrets = ["detect-secrets"]
 manifest = ["manifest-ml"]