title: How to make two markers share the same label in the legend using matplotlib?
body: <p>What I want is like this:
  <img src="https://i.stack.imgur.com/35FjA.jpg" alt="enter image description here"></p>
  
  <p>What I get is this:
  <img src="https://i.stack.imgur.com/HnoOU.png" alt="enter image description here"></p>
  
  <p>So how to merge the markers into one label?
  also for the lines, for the lines, of course, u can realize it by not assigning label to the second line while using the same linetype, but for the markers, you can not, since they are of different shapes.</p>