title: How to check whether a minor mode(.e.g flymake-mode) is on?
body: <p>I always get error when use flymake-mode. And flymake-mode turn off.</p>
  
  <p><img src="https://i.stack.imgur.com/2ybdz.jpg" alt="enter image description here"></p>
  
  <p>So I want to check whether flymake-mode is on. If it is not on, I will turn it on before call flymake-next-error.</p>
  
  <p>Thanks.</p>