input: from flask import Flask
  import datetime
  
  def get_current_datetime():
      """Returns the current date and time in the format "Year-Month-Day Hour:Minute:Second" as a string.
      Example:
      >>> get_current_datetime()
      '2023-10-05 14:30:45'
      """
      return datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
output:     return datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")