input: def get_current_datetime_web_api():
      """Create a web API with Python and Flask to give the current date and time.
      When accessed via a GET request to the '/datetime' route, the API should return 
      the current date and time formatted as 'YYYY-MM-DD HH:MM:SS'.
      Example:
      If the current date and time is '2023-10-05 14:30:45', then:
      GET /datetime --> '2023-10-05 14:30:45'
      """
output:     
      from flask import Flask, jsonify
      from datetime import datetime
  
      app = Flask(__name__)
  
      @app.route('/datetime', methods=['GET'])
      def get_datetime():
          current_datetime = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
          return jsonify(current_datetime)
  
      if __name__ == '__main__':
          app.run(debug=True)
  