input: from typing import Dict
  
  def get_current_datetime() -> Dict[str, 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".
      >>> from flask import Flask, request
      >>> app = Flask(__name__)
      >>> @app.route('/datetime')
      ... def get_datetime_endpoint():
      ...     from datetime import datetime
      ...     return datetime.now().strftime("%Y-%m-%d %H:%M:%S")
      >>> client = app.test_client()
      >>> response = client.get('/datetime')
      >>> response.status_code == 200
      True
      >>> '2023' in response.get_data(as_text=True)
      True
      """
output:     from datetime import datetime
      return {"current_datetime": datetime.now().strftime("%Y-%m-%d %H:%M:%S")}