title: Missing argument self when scheduling method
body: <p>I'd like to schedule a method using the schedule module but it doesn't work.</p>
  
  <p>The error message is as follows:</p>
  
  <blockquote>
    <p>Warning: Missing Argument 'self'.</p>
  </blockquote>
  
  <p>Here is my code:</p>
  
  <pre><code>def p_b(self):
      do
      print('hello')
      do
      do
  
  schedule.every().minute.do(p_b)
  
  while True:
      schedule.run_pending()  # error comes out. 
      time.sleep(1)
  </code></pre>