Docstrings: Module descriptions (#8262)

Added/changed the module descriptions (the firs-line docstrings in the
`__init__` files).
Added class hierarchy info.
 @baskaryan

libs/langchain/langchain/agents/__init__.py

@@ -1,4 +1,33 @@
-"""Interface for agents."""
+"""
+**Agent** is a class that uses an LLM to choose a sequence of actions to take.
+
+In Chains, a sequence of actions is hardcoded. In Agents,
+a language model is used as a reasoning engine to determine which actions
+to take and in which order.
+
+Agents select and use **Tools** and **Toolkits** for actions.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BaseSingleActionAgent --> LLMSingleActionAgent
+                              OpenAIFunctionsAgent
+                              XMLAgent
+                              Agent --> <name>Agent  # Examples: ZeroShotAgent, ChatAgent
+                                        
+
+    BaseMultiActionAgent  --> OpenAIMultiFunctionsAgent
+    
+    
+**Main helpers:**
+
+.. code-block::
+
+    AgentType, AgentExecutor, AgentOutputParser, AgentExecutorIterator,
+    AgentAction, AgentFinish
+    
+"""  # noqa: E501
 from langchain.agents.agent import (
     Agent,
     AgentExecutor,

libs/langchain/langchain/cache.py

@@ -1,4 +1,24 @@
-"""Beta Feature: base interface for cache."""
+"""
+.. warning::
+  Beta Feature!
+
+**Cache** provides an optional caching layer for LLMs.
+
+Cache is useful for two reasons:
+
+- It can save you money by reducing the number of API calls you make to the LLM
+  provider if you're often requesting the same completion multiple times.
+- It can speed up your application by reducing the number of API calls you make
+  to the LLM provider.
+
+Cache directly competes with Memory. See documentation for Pros and Cons.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BaseCache --> <name>Cache  # Examples: InMemoryCache, RedisCache, GPTCache
+"""
 from __future__ import annotations
 
 import hashlib

libs/langchain/langchain/callbacks/__init__.py

@@ -1,4 +1,11 @@
-"""Callback handlers that allow listening to events in LangChain."""
+"""**Callback handlers** allow listening to events in LangChain.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BaseCallbackHandler --> <name>CallbackHandler  # Example: AimCallbackHandler
+"""
 
 from langchain.callbacks.aim_callback import AimCallbackHandler
 from langchain.callbacks.argilla_callback import ArgillaCallbackHandler

libs/langchain/langchain/chains/__init__.py

@@ -1,16 +1,21 @@
-"""Chains are easily reusable components which can be linked together.
+"""**Chains** are easily reusable components linked together.
 
-    Chains should be used to encode a sequence of calls to components like
-    models, document retrievers, other chains, etc., and provide a simple interface
-    to this sequence.
+Chains encode a sequence of calls to components like models, document retrievers,
+other Chains, etc., and provide a simple interface to this sequence.
 
-    The Chain interface makes it easy to create apps that are:
-        - Stateful: add Memory to any Chain to give it state,
-        - Observable: pass Callbacks to a Chain to execute additional functionality,
-            like logging, outside the main sequence of component calls,
-        - Composable: the Chain API is flexible enough that it is easy to combine
-            Chains with other components, including other Chains.
-    """
+The Chain interface makes it easy to create apps that are:
+
+    - **Stateful:** add Memory to any Chain to give it state,
+    - **Observable:** pass Callbacks to a Chain to execute additional functionality,
+      like logging, outside the main sequence of component calls,
+    - **Composable:** combine Chains with other components, including other Chains.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    Chain --> <name>Chain  # Examples: LLMChain, MapReduceChain, RouterChain
+"""
 
 from langchain.chains.api.base import APIChain
 from langchain.chains.api.openapi.chain import OpenAPIEndpointChain

libs/langchain/langchain/chat_models/__init__.py

@@ -1,3 +1,22 @@
+"""**Chat Models** are a variation on language models.
+
+While Chat Models use language models under the hood, the interface they expose
+is a bit different. Rather than expose a "text in, text out" API, they expose
+an interface where "chat messages" are the inputs and outputs.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BaseLanguageModel --> BaseChatModel --> <name>  # Examples: ChatOpenAI, ChatGooglePalm
+
+**Main helpers:**
+
+.. code-block::
+
+    AIMessage, BaseMessage, HumanMessage
+"""  # noqa: E501
+
 from langchain.chat_models.anthropic import ChatAnthropic
 from langchain.chat_models.azure_openai import AzureChatOpenAI
 from langchain.chat_models.fake import FakeListChatModel

libs/langchain/langchain/docstore/__init__.py

@@ -1,4 +1,19 @@
-"""Wrappers on top of docstores."""
+"""**Docstores** are classes to store and load Documents.
+
+The **Docstore** is a simplified version of the Document Loader.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    Docstore --> <name> # Examples: InMemoryDocstore, Wikipedia
+
+**Main helpers:**
+
+.. code-block::
+
+    Document, AddableMixin
+"""
 from langchain.docstore.arbitrary_fn import DocstoreFn
 from langchain.docstore.in_memory import InMemoryDocstore
 from langchain.docstore.wikipedia import Wikipedia

libs/langchain/langchain/document_loaders/__init__.py

@@ -1,4 +1,19 @@
-"""All different types of document loaders."""
+"""**Document Loaders**  are classes to load Documents.
+
+**Document Loaders** are usually used to load a lot of Documents in a single run.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BaseLoader --> <name>Loader  # Examples: TextLoader, UnstructuredFileLoader
+
+**Main helpers:**
+
+.. code-block::
+
+    Document, <name>TextSplitter
+"""
 
 from langchain.document_loaders.acreom import AcreomLoader
 from langchain.document_loaders.airbyte_json import AirbyteJSONLoader

libs/langchain/langchain/document_transformers/__init__.py

@@ -1,3 +1,20 @@
+"""**Document Transformers** are classes to transform Documents.
+
+**Document Transformers** usually used to transform a lot of Documents in a single run.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BaseDocumentTransformer --> <name>  # Examples: DoctranQATransformer, DoctranTextTranslator
+
+**Main helpers:**
+
+.. code-block::
+
+    Document
+"""  # noqa: E501
+
 from langchain.document_transformers.doctran_text_extract import (
     DoctranPropertyExtractor,
 )
@@ -10,6 +27,7 @@
 )
 from langchain.document_transformers.html2text import Html2TextTransformer
 from langchain.document_transformers.long_context_reorder import LongContextReorder
+from langchain.document_transformers.openai_functions import OpenAIMetadataTagger
 
 __all__ = [
     "DoctranQATransformer",
@@ -22,5 +40,3 @@
     "OpenAIMetadataTagger",
     "Html2TextTransformer",
 ]
-
-from langchain.document_transformers.openai_functions import OpenAIMetadataTagger

libs/langchain/langchain/embeddings/__init__.py

@@ -1,4 +1,16 @@
-"""Wrappers around embedding modules."""
+"""**Embedding models**  are wrappers around embedding models
+from different APIs and services.
+
+**Embedding models** can be LLMs or not.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    Embeddings --> <name>Embeddings  # Examples: OpenAIEmbeddings, HuggingFaceEmbeddings
+"""
+
+
 import logging
 from typing import Any
 

libs/langchain/langchain/env.py

@@ -4,7 +4,7 @@
 
 @lru_cache(maxsize=1)
 def get_runtime_environment() -> dict:
-    """Get information about the environment."""
+    """Get information about the LangChain runtime environment."""
     # Lazy import to avoid circular imports
     from langchain import __version__
 

libs/langchain/langchain/evaluation/__init__.py

@@ -1,4 +1,4 @@
-"""Evaluation chains for grading LLM and Chain outputs.
+"""**Evaluation** chains for grading LLM and Chain outputs.
 
 This module contains off-the-shelf evaluation chains for grading the output of
 LangChain primitives such as language models and chains.

libs/langchain/langchain/graphs/__init__.py

@@ -1,4 +1,5 @@
-"""Graph implementations."""
+"""**Graphs** provide a natural language interface to graph databases."""
+
 from langchain.graphs.arangodb_graph import ArangoGraph
 from langchain.graphs.hugegraph import HugeGraph
 from langchain.graphs.kuzu_graph import KuzuGraph

libs/langchain/langchain/indexes/__init__.py

@@ -1,4 +1,4 @@
-"""All index utils."""
+"""**Index** utilities."""
 from langchain.indexes.graph import GraphIndexCreator
 from langchain.indexes.vectorstore import VectorstoreIndexCreator
 

libs/langchain/langchain/llms/__init__.py

@@ -1,4 +1,22 @@
-"""Access to the large language model APIs and services."""
+"""
+**LLM** classes provide
+access to the large language model (**LLM**) APIs and services.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BaseLanguageModel --> BaseLLM --> LLM --> <name>  # Examples: AI21, HuggingFaceHub, OpenAI
+
+**Main helpers:**
+
+.. code-block::
+
+    LLMResult, PromptValue,
+    CallbackManagerForLLMRun, AsyncCallbackManagerForLLMRun,
+    CallbackManager, AsyncCallbackManager,
+    AIMessage, BaseMessage
+"""  # noqa: E501
 from typing import Dict, Type
 
 from langchain.llms.ai21 import AI21

libs/langchain/langchain/load/__init__.py

@@ -0,0 +1 @@
+"""Serialization and deserialization."""

libs/langchain/langchain/memory/__init__.py

@@ -1,4 +1,31 @@
-"""Memory maintains Chain state, incorporating context from past runs."""
+"""**Memory** maintains Chain state, incorporating context from past runs.
+
+**Class hierarchy for Memory:**
+
+.. code-block::
+
+    BaseMemory --> BaseChatMemory --> <name>Memory  # Examples: ZepMemory, MotorheadMemory
+
+**Main helpers:**
+
+.. code-block::
+
+    BaseChatMessageHistory
+
+**Chat Message History** stores the chat message history in different stores.
+
+**Class hierarchy for ChatMessageHistory:**
+
+.. code-block::
+
+    BaseChatMessageHistory --> <name>ChatMessageHistory  # Example: ZepChatMessageHistory
+
+**Main helpers:**
+
+.. code-block::
+
+    AIMessage, BaseMessage, HumanMessage
+"""  # noqa: E501
 from langchain.memory.buffer import (
     ConversationBufferMemory,
     ConversationStringBufferMemory,

libs/langchain/langchain/output_parsers/__init__.py

@@ -1,3 +1,17 @@
+"""**OutputParser** classes parse the output of an LLM call.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BaseLLMOutputParser --> BaseOutputParser --> <name>OutputParser  # ListOutputParser, PydanticOutputParser
+
+**Main helpers:**
+
+.. code-block::
+
+    Serializable, Generation, PromptValue
+"""  # noqa: E501
 from langchain.output_parsers.boolean import BooleanOutputParser
 from langchain.output_parsers.combining import CombiningOutputParser
 from langchain.output_parsers.datetime import DatetimeOutputParser

libs/langchain/langchain/prompts/__init__.py

@@ -1,4 +1,32 @@
-"""Prompt template classes."""
+"""**Prompt** is the input to the model.
+
+Prompt is often constructed
+from multiple components. Prompt classes and functions make constructing
+ and working with prompts easy.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BasePromptTemplate --> PipelinePromptTemplate
+                           StringPromptTemplate --> PromptTemplate
+                                                    FewShotPromptTemplate
+                                                    FewShotPromptWithTemplates
+                           BaseChatPromptTemplate --> AutoGPTPrompt
+                                                      ChatPromptTemplate --> AgentScratchPadChatPromptTemplate
+
+
+
+    BaseMessagePromptTemplate --> MessagesPlaceholder
+                                  BaseStringMessagePromptTemplate --> ChatMessagePromptTemplate
+                                                                      HumanMessagePromptTemplate
+                                                                      AIMessagePromptTemplate
+                                                                      SystemMessagePromptTemplate
+
+    PromptValue --> StringPromptValue
+                    ChatPromptValue
+
+"""  # noqa: E501
 from langchain.prompts.base import StringPromptTemplate
 from langchain.prompts.chat import (
     AIMessagePromptTemplate,

libs/langchain/langchain/retrievers/__init__.py

@@ -1,3 +1,23 @@
+"""**Retriever** class returns Documents given a text **query**.
+
+It is more general than a vector store. A retriever does not need to be able to
+store documents, only to return (or retrieve) it. Vector stores can be used as
+the backbone of a retriever, but there are other types of retrievers as well.
+
+**Class hierarchy:**
+
+.. code-block::
+
+    BaseRetriever --> <name>Retriever  # Examples: ArxivRetriever, MergerRetriever
+
+**Main helpers:**
+
+.. code-block::
+
+    Document, Serializable, Callbacks,
+    CallbackManagerForRetrieverRun, AsyncCallbackManagerForRetrieverRun
+"""
+
 from langchain.retrievers.arxiv import ArxivRetriever
 from langchain.retrievers.azure_cognitive_search import AzureCognitiveSearchRetriever
 from langchain.retrievers.bm25 import BM25Retriever

libs/langchain/langchain/schema/__init__.py

@@ -1,3 +1,4 @@
+"""**Schemas** are the LangChain Base Classes and Interfaces."""
 from langchain.schema.agent import AgentAction, AgentFinish
 from langchain.schema.document import BaseDocumentTransformer, Document
 from langchain.schema.memory import BaseChatMessageHistory, BaseMemory

libs/langchain/langchain/smith/__init__.py

@@ -1,4 +1,4 @@
-"""LangSmith utilities.
+"""**LangSmith** utilities.
 
 This module provides utilities for connecting to `LangSmith <https://smith.langchain.com/>`_. For more information on LangSmith, see the `LangSmith documentation <https://docs.smith.langchain.com/>`_.