input: Write a function to generate an HTML form with a submit button to send information to a Python program. The function should return the HTML code as a string.
  assert generate_html_form("action.py")=='<form action="action.py" method="post"><input type="submit" value="Submit"></form>'
  assert generate_html_form("process.py")=='<form action="process.py" method="post"><input type="submit" value="Submit"></form>'
  assert generate_html_form("")=='<form action="" method="post"><input type="submit" value="Submit"></form>'
output: def generate_html_form(action):
      return f'<form action="{action}" method="post"><input type="submit" value="Submit"></form>'