input: Write a function to generate an HTML form with a submit button that sends information to a Python program. The form should use the POST method and have an action attribute pointing to "action.py". If the function is called without any parameters, it should return the HTML form as a string.
  
  assert generate_html_form()=='<form action="action.py" method="post"><input type="submit" value="Submit"></form>'
output: def generate_html_form():
      return '<form action="action.py" method="post"><input type="submit" value="Submit"></form>'