input: 
  def get_current_datetime_api() -> str:
      """Create a web API with Python and Flask to give the current date and time.
      The API should return the current date and time in the format "YYYY-MM-DD HH:MM:SS".
  
      Example:
      for get_current_datetime_api() == '2023-10-05 14:30:00'
      """
  
output:     
      from flask import Flask, jsonify
      from datetime import datetime
  
      app = Flask(__name__)
  
      @app.route('/current_datetime', methods=['GET'])
      def current_datetime():
          now = datetime.now()
          formatted_datetime = now.strftime("%Y-%m-%d %H:%M:%S")
          return jsonify({"current_datetime": formatted_datetime})
  
      if __name__ == '__main__':
          app.run(debug=True)
  