input: 
  def get_current_datetime() -> str:
      """ Create a web API with Python and Flask to give the current date and time.
      >>> 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")
      >>> app.run()
      '2023-10-05 14:30:45'
      """
  
output:     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")
  
      if __name__ == "__main__":
          app.run()