add async support for anthropic (#2114)

should not be merged in before
https://github.com/anthropics/anthropic-sdk-python/pull/11 gets released

tests/integration_tests/llms/test_anthropic.py

@@ -1,9 +1,11 @@
 """Test Anthropic API wrapper."""
-
 from typing import Generator
 
+import pytest
+
 from langchain.callbacks.base import CallbackManager
 from langchain.llms.anthropic import Anthropic
+from langchain.schema import LLMResult
 from tests.unit_tests.callbacks.fake_callback_handler import FakeCallbackHandler
 
 
@@ -37,3 +39,27 @@ def test_anthropic_streaming_callback() -> None:
     )
     llm("Write me a sentence with 100 words.")
     assert callback_handler.llm_streams > 1
+
+
+@pytest.mark.asyncio
+async def test_anthropic_async_generate() -> None:
+    """Test async generate."""
+    llm = Anthropic()
+    output = await llm.agenerate(["How many toes do dogs have?"])
+    assert isinstance(output, LLMResult)
+
+
+@pytest.mark.asyncio
+async def test_anthropic_async_streaming_callback() -> None:
+    """Test that streaming correctly invokes on_llm_new_token callback."""
+    callback_handler = FakeCallbackHandler()
+    callback_manager = CallbackManager([callback_handler])
+    llm = Anthropic(
+        model="claude-v1",
+        streaming=True,
+        callback_manager=callback_manager,
+        verbose=True,
+    )
+    result = await llm.agenerate(["How many toes do dogs have?"])
+    assert callback_handler.llm_streams > 1
+    assert isinstance(result, LLMResult)