input: Write a function to generate an HTML form with a submit button that sends information to a specified Python program via a POST request. If the provided action URL and submit button text are valid, return the generated HTML form as a string. If any of the inputs are invalid, return an empty string.
  
  assert generate_html_form("action.py", "Submit")=="<form action='action.py' method='post'><input type='submit' value='Submit'></form>"
  assert generate_html_form("submit.php", "Send Data")=="<form action='submit.php' method='post'><input type='submit' value='Send Data'></form>"
  assert generate_html_form("", "Submit")==""
  assert generate_html_form("action.py", "")==""
  assert generate_html_form("", "")==""
output: def generate_html_form(action_url, submit_text):
      if action_url and submit_text:
          return f"<form action='{action_url}' method='post'><input type='submit' value='{submit_text}'></form>"
      else:
          return ""