input: Write a python function to create a Flask application and configure a SQLAlchemy database.
  assert 'SECRET_KEY' in app.config
  assert isinstance(db, SQLAlchemy)
  assert '<title>My App</title>' in render_template_string("<html><head><title>My App</title></head><body></body></html>")
output: def create_app():
      from flask import Flask, render_template_string
      from flask_sqlalchemy import SQLAlchemy
  
      app = Flask(__name__)
      app.config['SECRET_KEY'] = 'mysecretkey'
      app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///:memory:'
      
      db = SQLAlchemy(app)
  
      @app.route('/')
      def index():
          return render_template_string("<html><head><title>My App</title></head><body></body></html>")
  
      return app, db