input: def get_current_datetime() -> str:
      """ Create a web API with Python and Flask to give the current date and time.
      >>> get_current_datetime()
      '2023-10-05 14:30:45'
      """
      from flask import Flask
      import datetime
  
      app = Flask(__name__)
  
      @app.route('/datetime')
      def get_datetime():
          return datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
  
      return datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
  
  if __name__ == '__main__':
      app.run()
output:     if __name__ == '__main__':
          app.run()