input: 
  from flask import Flask
  import datetime
  
  app = Flask(__name__)
  
  @app.route('/datetime')
  def get_datetime():
      """ Create a web API using Flask to return the current date and time in the format
      YYYY-MM-DD HH:MM:SS.
      >>> get_datetime()
      '2023-10-05 14:32:15'
      """
      return datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
  
  if __name__ == '__main__':
      app.run()
  
output:     
      return datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
  