input: 
  from flask import Flask
  import datetime
  
  app = Flask(__name__)
  
  @app.route('/datetime')
  def get_datetime():
      """Create a web API with Python and Flask to give the current date and time.
      Returns the current date and time formatted as 'YYYY-MM-DD HH:MM:SS'.
      Example:
      When accessed at /datetime, the API should return something like '2023-10-05 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")