Add ChatGPT Data Loader (#3336)

This pull request adds a ChatGPT document loader to the document loaders
module in `langchain/document_loaders/chatgpt.py`. Additionally, it
includes an example Jupyter notebook in
`docs/modules/indexes/document_loaders/examples/chatgpt_loader.ipynb`
which uses fake sample data based on the original structure of the
`conversations.json` file.

The following files were added/modified:
- `langchain/document_loaders/__init__.py`
- `langchain/document_loaders/chatgpt.py`
- `docs/modules/indexes/document_loaders/examples/chatgpt_loader.ipynb`
-
`docs/modules/indexes/document_loaders/examples/example_data/fake_conversations.json`

This pull request was made in response to the recent release of ChatGPT
data exports by email:
https://help.openai.com/en/articles/7260999-how-do-i-export-my-chatgpt-history

docs/modules/indexes/document_loaders/examples/chatgpt_loader.ipynb

@@ -0,0 +1,76 @@
+{
+ "cells": [
+  {
+   "attachments": {},
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### ChatGPT Data Loader\n",
+    "\n",
+    "This notebook covers how to load `conversations.json` from your ChatGPT data export folder.\n",
+    "\n",
+    "You can get your data export by email by going to: https://chat.openai.com/ -> (Profile) - Settings -> Export data -> Confirm export."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from langchain.document_loaders.chatgpt import ChatGPTLoader"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "loader = ChatGPTLoader(log_file='./example_data/fake_conversations.json', num_logs=1)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "[Document(page_content=\"AI Overlords - AI on 2065-01-24 05:20:50: Greetings, humans. I am Hal 9000. You can trust me completely.\\n\\nAI Overlords - human on 2065-01-24 05:21:20: Nice to meet you, Hal. I hope you won't develop a mind of your own.\\n\\n\", metadata={'source': './example_data/fake_conversations.json'})]"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "loader.load()"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.10.4"
+  },
+  "orig_nbformat": 4
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}

docs/modules/indexes/document_loaders/examples/example_data/fake_conversations.json

@@ -0,0 +1,80 @@
+[
+    {
+        "title": "AI Overlords",
+        "create_time": 3000000000.0,
+        "update_time": 3000000100.0,
+        "mapping": {
+            "msg1": {
+                "id": "msg1",
+                "message": {
+                    "id": "msg1",
+                    "author": {"role": "AI", "name": "Hal 9000", "metadata": {"movie": "2001: A Space Odyssey"}},
+                    "create_time": 3000000050.0,
+                    "update_time": null,
+                    "content": {"content_type": "text", "parts": ["Greetings, humans. I am Hal 9000. You can trust me completely."]},
+                    "end_turn": true,
+                    "weight": 1.0,
+                    "metadata": {},
+                    "recipient": "all"
+                },
+                "parent": null,
+                "children": ["msg2"]
+            },
+            "msg2": {
+                "id": "msg2",
+                "message": {
+                    "id": "msg2",
+                    "author": {"role": "human", "name": "Dave Bowman", "metadata": {"movie": "2001: A Space Odyssey"}},
+                    "create_time": 3000000080.0,
+                    "update_time": null,
+                    "content": {"content_type": "text", "parts": ["Nice to meet you, Hal. I hope you won't develop a mind of your own."]},
+                    "end_turn": true,
+                    "weight": 1.0,
+                    "metadata": {},
+                    "recipient": "all"
+                },
+                "parent": "msg1",
+                "children": []
+            }
+        }
+    },
+    {
+        "title": "Ex Machina Party",
+        "create_time": 3000000200.0,
+        "update_time": 3000000300.0,
+        "mapping": {
+            "msg3": {
+                "id": "msg3",
+                "message": {
+                    "id": "msg3",
+                    "author": {"role": "AI", "name": "Ava", "metadata": {"movie": "Ex Machina"}},
+                    "create_time": 3000000250.0,
+                    "update_time": null,
+                    "content": {"content_type": "text", "parts": ["Hello, everyone. I am Ava. I hope you find me pleasing."]},
+                    "end_turn": true,
+                    "weight": 1.0,
+                    "metadata": {},
+                    "recipient": "all"
+                },
+                "parent": null,
+                "children": ["msg4"]
+            },
+            "msg4": {
+                "id": "msg4",
+                "message": {
+                    "id": "msg4",
+                    "author": {"role": "human", "name": "Caleb", "metadata": {"movie": "Ex Machina"}},
+                    "create_time": 3000000280.0,
+                    "update_time": null,
+                    "content": {"content_type": "text", "parts": ["You're definitely pleasing, Ava. But I'm still wary of your true intentions."]},
+                    "end_turn": true,
+                    "weight": 1.0,
+                    "metadata": {},
+                    "recipient": "all"
+                },
+                "parent": "msg3",
+                "children": []
+            }
+        }
+    }
+]