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.
      Example:
      When accessing the endpoint '/datetime' at 2022-10-15 14:30:45, the response should be '2022-10-15 14:30:45'.
      """
      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")
  