input: Write a function to create a new post in a MongoDB database using Flask and Flask-PyMongo.
  assert create_post({"title": "First Post", "body": "This is the first post."}) == {"id": "1", "title": "First Post", "body": "This is the first post."}
  assert create_post({"title": "Second Post", "body": "This is the second post."}) == {"id": "2", "title": "Second Post", "body": "This is the second post."}
  assert create_post({"title": "Third Post", "body": "This is the third post."}) == {"id": "3", "title": "Third Post", "body": "This is the third post."}
output: from flask import Flask, request, jsonify
  from flask_pymongo import PyMongo
  from bson.objectid import ObjectId
  
  app = Flask(__name__)
  app.config["MONGO_URI"] = "mongodb://localhost:27017/myDatabase"
  mongo = PyMongo(app)
  
  def create_post(post_data):
      post_id = mongo.db.posts.insert_one(post_data).inserted_id
      post = mongo.db.posts.find_one({"_id": ObjectId(post_id)})
      return {"id": str(post["_id"]), "title": post["title"], "body": post["body"]}
  
  if __name__ == "__main__":
      app.run(debug=True)