mongodb doc loader init (#10645)

- **Description:** A Document Loader for MongoDB
  - **Issue:** n/a
  - **Dependencies:** Motor, the async driver for MongoDB
  - **Tag maintainer:** n/a
  - **Twitter handle:** pigpenblue

Note that an initial mongodb document loader was created 4 months ago,
but the [PR ](https://github.com/langchain-ai/langchain/pull/4285)was
never pulled in. @leo-gan had commented on that PR, but given it is
extremely far behind the master branch and a ton has changed in
Langchain since then (including repo name and structure), I rewrote the
branch and issued a new PR with the expectation that the old one can be
closed.

Please reference that old PR for comments/context, but it can be closed
in favor of this one. Thanks!

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>
Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

docs/extras/integrations/document_loaders/mongodb.ipynb

@@ -0,0 +1,163 @@
+{
+ "cells": [
+  {
+   "attachments": {},
+   "cell_type": "markdown",
+   "metadata": {
+    "id": "vm8vn9t8DvC_"
+   },
+   "source": [
+    "# MongoDB"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "[MongoDB](https://www.mongodb.com/) is a NoSQL , document-oriented database that supports JSON-like documents with a dynamic schema."
+   ]
+  },
+  {
+   "attachments": {},
+   "cell_type": "markdown",
+   "metadata": {
+    "id": "5WjXERXzFEhg"
+   },
+   "source": [
+    "## Overview"
+   ]
+  },
+  {
+   "attachments": {},
+   "cell_type": "markdown",
+   "metadata": {
+    "id": "juAmbgoWD17u"
+   },
+   "source": [
+    "The MongoDB Document Loader returns a list of Langchain Documents from a MongoDB database.\n",
+    "\n",
+    "The Loader requires the following parameters:\n",
+    "\n",
+    "*   MongoDB connection string\n",
+    "*   MongoDB database name\n",
+    "*   MongoDB collection name\n",
+    "*   (Optional) Content Filter dictionary\n",
+    "\n",
+    "The output takes the following format:\n",
+    "\n",
+    "- pageContent= Mongo Document\n",
+    "- metadata={'database': '[database_name]', 'collection': '[collection_name]'}"
+   ]
+  },
+  {
+   "attachments": {},
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Load the Document Loader"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 24,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# add this import for running in jupyter notebook\n",
+    "import nest_asyncio\n",
+    "nest_asyncio.apply()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from langchain.document_loaders.mongodb import MongodbLoader"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 25,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "loader = MongodbLoader(connection_string=\"mongodb://localhost:27017/\",\n",
+    "                       db_name=\"sample_restaurants\", \n",
+    "                       collection_name=\"restaurants\",\n",
+    "                       filter_criteria={\"borough\": \"Bronx\", \"cuisine\": \"Bakery\" },\n",
+    "                       ) "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 26,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "25359"
+      ]
+     },
+     "execution_count": 26,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "docs = loader.load()\n",
+    "\n",
+    "len(docs)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 27,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "Document(page_content=\"{'_id': ObjectId('5eb3d668b31de5d588f4292a'), 'address': {'building': '2780', 'coord': [-73.98241999999999, 40.579505], 'street': 'Stillwell Avenue', 'zipcode': '11224'}, 'borough': 'Brooklyn', 'cuisine': 'American', 'grades': [{'date': datetime.datetime(2014, 6, 10, 0, 0), 'grade': 'A', 'score': 5}, {'date': datetime.datetime(2013, 6, 5, 0, 0), 'grade': 'A', 'score': 7}, {'date': datetime.datetime(2012, 4, 13, 0, 0), 'grade': 'A', 'score': 12}, {'date': datetime.datetime(2011, 10, 12, 0, 0), 'grade': 'A', 'score': 12}], 'name': 'Riviera Caterer', 'restaurant_id': '40356018'}\", metadata={'database': 'sample_restaurants', 'collection': 'restaurants'})"
+      ]
+     },
+     "execution_count": 27,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "docs[0]"
+   ]
+  }
+ ],
+ "metadata": {
+  "colab": {
+   "collapsed_sections": [
+    "5WjXERXzFEhg"
+   ],
+   "provenance": []
+  },
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "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": "3.9.18"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}