add load() deserializer function that bypasses need for json serialization (#7626)

There is already a `loads()` function which takes a JSON string and
loads it using the Reviver

But in the callbacks system, there is a `serialized` object that is
passed in and that object is already a deserialized JSON-compatible
object. This allows you to call `load(serialized)` and bypass
intermediate JSON encoding.

I found one other place in the code that benefited from this
short-circuiting (string_run_evaluator.py) so I fixed that too.

Tagging @baskaryan for general/utility stuff.

<!-- Thank you for contributing to LangChain!

Replace this comment with:
  - Description: a description of the change, 
  - Issue: the issue # it fixes (if applicable),
  - Dependencies: any dependencies required for this change,
- Tag maintainer: for a quicker response, tag the relevant maintainer
(see below),
- Twitter handle: we announce bigger features on Twitter. If your PR
gets announced and you'd like a mention, we'll gladly shout you out!

If you're adding a new integration, please include:
1. a test for the integration, preferably unit tests that do not rely on
network access,
  2. an example notebook showing its use.

Maintainer responsibilities:
  - General / Misc / if you don't know who to tag: @baskaryan
  - DataLoaders / VectorStores / Retrievers: @rlancemartin, @eyurtsev
  - Models / Prompts: @hwchase17, @baskaryan
  - Memory: @hwchase17
  - Agents / Tools / Toolkits: @hinthornw
  - Tracing / Callbacks: @agola11
  - Async: @agola11

If no one reviews your PR within a few days, feel free to @-mention the
same people again.

See contribution guidelines for more information on how to write/run
tests, lint, etc:
https://github.com/hwchase17/langchain/blob/master/.github/CONTRIBUTING.md
 -->

---------

Co-authored-by: Nuno Campos <nuno@boringbits.io>

libs/langchain/langchain/load/load.py

@@ -55,7 +55,7 @@ class Reviver:
                 raise ValueError(f"Invalid namespace: {value}")
 
             # The root namespace "langchain" is not a valid identifier.
-            if len(namespace) == 1:
+            if len(namespace) == 1 and namespace[0] == "langchain":
                 raise ValueError(f"Invalid namespace: {value}")
 
             mod = importlib.import_module(".".join(namespace))
@@ -79,7 +79,8 @@ def loads(
     secrets_map: Optional[Dict[str, str]] = None,
     valid_namespaces: Optional[List[str]] = None,
 ) -> Any:
-    """Load a JSON object from a string.
+    """Revive a LangChain class from a JSON string.
+    Equivalent to `load(json.loads(text))`.
 
     Args:
         text: The string to load.
@@ -88,6 +89,38 @@ def loads(
             to allow to be deserialized.
 
     Returns:
-
+        Revived LangChain objects.
     """
     return json.loads(text, object_hook=Reviver(secrets_map, valid_namespaces))
+
+
+def load(
+    obj: Any,
+    *,
+    secrets_map: Optional[Dict[str, str]] = None,
+    valid_namespaces: Optional[List[str]] = None,
+) -> Any:
+    """Revive a LangChain class from a JSON object. Use this if you already
+    have a parsed JSON object, eg. from `json.load` or `orjson.loads`.
+
+    Args:
+        obj: The object to load.
+        secrets_map: A map of secrets to load.
+        valid_namespaces: A list of additional namespaces (modules)
+            to allow to be deserialized.
+
+    Returns:
+        Revived LangChain objects.
+    """
+    reviver = Reviver(secrets_map, valid_namespaces)
+
+    def _load(obj: Any) -> Any:
+        if isinstance(obj, dict):
+            # Need to revive leaf nodes before reviving this node
+            loaded_obj = {k: _load(v) for k, v in obj.items()}
+            return reviver(loaded_obj)
+        if isinstance(obj, list):
+            return [_load(o) for o in obj]
+        return obj
+
+    return _load(obj)

libs/langchain/langchain/smith/evaluation/string_run_evaluator.py

@@ -13,8 +13,8 @@ from langchain.callbacks.manager import (
 )
 from langchain.chains.base import Chain
 from langchain.evaluation.schema import StringEvaluator
-from langchain.load.dump import dumps
+from langchain.load.dump import dumpd
-from langchain.load.load import loads
+from langchain.load.load import load
 from langchain.load.serializable import Serializable
 from langchain.schema import RUN_KEY, messages_from_dict
 from langchain.schema.messages import BaseMessage, get_buffer_string
@@ -25,7 +25,7 @@ def _get_messages_from_run_dict(messages: List[dict]) -> List[BaseMessage]:
         return []
     first_message = messages[0]
     if "lc" in first_message:
-        return [loads(dumps(message)) for message in messages]
+        return [load(dumpd(message)) for message in messages]
     else:
         return messages_from_dict(messages)
 

libs/langchain/tests/unit_tests/load/test_load.py

@@ -4,8 +4,8 @@ import pytest
 
 from langchain.chains.llm import LLMChain
 from langchain.llms.openai import OpenAI
-from langchain.load.dump import dumps
+from langchain.load.dump import dumpd, dumps
-from langchain.load.load import loads
+from langchain.load.load import load, loads
 from langchain.prompts.prompt import PromptTemplate
 
 
@@ -14,7 +14,7 @@ class NotSerializable:
 
 
 @pytest.mark.requires("openai")
-def test_load_openai_llm() -> None:
+def test_loads_openai_llm() -> None:
     llm = OpenAI(model="davinci", temperature=0.5, openai_api_key="hello")
     llm_string = dumps(llm)
     llm2 = loads(llm_string, secrets_map={"OPENAI_API_KEY": "hello"})
@@ -25,7 +25,7 @@ def test_load_openai_llm() -> None:
 
 
 @pytest.mark.requires("openai")
-def test_load_llmchain() -> None:
+def test_loads_llmchain() -> None:
     llm = OpenAI(model="davinci", temperature=0.5, openai_api_key="hello")
     prompt = PromptTemplate.from_template("hello {name}!")
     chain = LLMChain(llm=llm, prompt=prompt)
@@ -40,7 +40,7 @@ def test_load_llmchain() -> None:
 
 
 @pytest.mark.requires("openai")
-def test_load_llmchain_env() -> None:
+def test_loads_llmchain_env() -> None:
     import os
 
     has_env = "OPENAI_API_KEY" in os.environ
@@ -64,7 +64,7 @@ def test_load_llmchain_env() -> None:
 
 
 @pytest.mark.requires("openai")
-def test_load_llmchain_with_non_serializable_arg() -> None:
+def test_loads_llmchain_with_non_serializable_arg() -> None:
     llm = OpenAI(
         model="davinci",
         temperature=0.5,
@@ -76,3 +76,68 @@ def test_load_llmchain_with_non_serializable_arg() -> None:
     chain_string = dumps(chain, pretty=True)
     with pytest.raises(NotImplementedError):
         loads(chain_string, secrets_map={"OPENAI_API_KEY": "hello"})
+
+
+@pytest.mark.requires("openai")
+def test_load_openai_llm() -> None:
+    llm = OpenAI(model="davinci", temperature=0.5, openai_api_key="hello")
+    llm_obj = dumpd(llm)
+    llm2 = load(llm_obj, secrets_map={"OPENAI_API_KEY": "hello"})
+
+    assert llm2 == llm
+    assert dumpd(llm2) == llm_obj
+    assert isinstance(llm2, OpenAI)
+
+
+@pytest.mark.requires("openai")
+def test_load_llmchain() -> None:
+    llm = OpenAI(model="davinci", temperature=0.5, openai_api_key="hello")
+    prompt = PromptTemplate.from_template("hello {name}!")
+    chain = LLMChain(llm=llm, prompt=prompt)
+    chain_obj = dumpd(chain)
+    chain2 = load(chain_obj, secrets_map={"OPENAI_API_KEY": "hello"})
+
+    assert chain2 == chain
+    assert dumpd(chain2) == chain_obj
+    assert isinstance(chain2, LLMChain)
+    assert isinstance(chain2.llm, OpenAI)
+    assert isinstance(chain2.prompt, PromptTemplate)
+
+
+@pytest.mark.requires("openai")
+def test_load_llmchain_env() -> None:
+    import os
+
+    has_env = "OPENAI_API_KEY" in os.environ
+    if not has_env:
+        os.environ["OPENAI_API_KEY"] = "env_variable"
+
+    llm = OpenAI(model="davinci", temperature=0.5)
+    prompt = PromptTemplate.from_template("hello {name}!")
+    chain = LLMChain(llm=llm, prompt=prompt)
+    chain_obj = dumpd(chain)
+    chain2 = load(chain_obj)
+
+    assert chain2 == chain
+    assert dumpd(chain2) == chain_obj
+    assert isinstance(chain2, LLMChain)
+    assert isinstance(chain2.llm, OpenAI)
+    assert isinstance(chain2.prompt, PromptTemplate)
+
+    if not has_env:
+        del os.environ["OPENAI_API_KEY"]
+
+
+@pytest.mark.requires("openai")
+def test_load_llmchain_with_non_serializable_arg() -> None:
+    llm = OpenAI(
+        model="davinci",
+        temperature=0.5,
+        openai_api_key="hello",
+        client=NotSerializable,
+    )
+    prompt = PromptTemplate.from_template("hello {name}!")
+    chain = LLMChain(llm=llm, prompt=prompt)
+    chain_obj = dumpd(chain)
+    with pytest.raises(NotImplementedError):
+        load(chain_obj, secrets_map={"OPENAI_API_KEY": "hello"})