input: 
  from flask import Flask
  import datetime
  
  app = Flask(__name__)
  
  @app.route('/datetime')
  def get_datetime():
      """
      A web API using Flask to return the current date and time in the format "YYYY-MM-DD HH:MM:SS".
      Example:
      For the route '/datetime', the API should return the current date and time.
      For example, if the current date and time is 2023-10-15 14:30:45, the response should be:
      "2023-10-15 14:30:45"
      """
      return datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
  
  if __name__ == '__main__':
      app.run()
  
output:     
      current_time = datetime.datetime.now()
      formatted_time = current_time.strftime("%Y-%m-%d %H:%M:%S")
      return formatted_time
  