pal chain (#207)

from https://arxiv.org/pdf/2211.10435.pdf

tests/integration_tests/chains/test_pal.py

@@ -0,0 +1,31 @@
+"""Test PAL chain."""
+
+from langchain import OpenAI
+from langchain.chains.pal.base import PALChain
+
+
+def test_math_prompt() -> None:
+    """Test math prompt."""
+    llm = OpenAI(model_name="code-davinci-002", temperature=0, max_tokens=512)
+    pal_chain = PALChain.from_math_prompt(llm)
+    question = (
+        "Jan has three times the number of pets as Marcia. "
+        "Marcia has two more pets than Cindy. "
+        "If Cindy has four pets, how many total pets do the three have?"
+    )
+    output = pal_chain.run(question)
+    assert output == "28"
+
+
+def test_colored_object_prompt() -> None:
+    """Test colored object prompt."""
+    llm = OpenAI(model_name="code-davinci-002", temperature=0, max_tokens=512)
+    pal_chain = PALChain.from_colored_object_prompt(llm)
+    question = (
+        "On the desk, you see two blue booklets, "
+        "two purple booklets, and two yellow pairs of sunglasses. "
+        "If I remove all the pairs of sunglasses from the desk, "
+        "how many purple items remain on it?"
+    )
+    output = pal_chain.run(question)
+    assert output == "2"