title: How to add annotation arrows to legend
body: <p>I have a trajectory of some robot, together with some arrows describing parameters of the robot. Just like so:
  <a href="https://i.stack.imgur.com/YZtv6.png" rel="nofollow noreferrer">Robot Trajectory with annotation arrows</a>
  (because of my lack of reputation, I cannot add the picture directly)</p>
  
  <p>The question is: How can I display the annotation arrows together with the lines in the legend?</p>
  
  <p>I use annotation arrows in order to draw the arrows as per this <a href="https://stackoverflow.com/questions/57221054/how-to-draw-scale-independent-arrows-with-matplotlib">answer</a> in a loop to draw arrows for every point.
  Here is the code for one of my annotations:</p>
  
  <pre class="lang-py prettyprint-override"><code>an = ax.annotate('', xy=xy_tuple, xytext=xy_texttuple, label=labelString, arrowprops=dict(color=arrowcolor, arrowstyle=aStyle))
  </code></pre>
  
  <p>And just as a reference, I use the plotting function like so:</p>
  
  <pre class="lang-py prettyprint-override"><code>    # plot Local x-y axis
      fig, ax1 = plt.subplots()
      ln1 = ax1.plot(x, y, '-o', label='Location of the last 48h')
      ax1.set_ylabel('Local North (m)')
      ax1.set_xlabel('Local East (m)')
      ax1.grid()
      fig.gca().set_aspect('equal', adjustable='box')
      lns = ln1
      labs = [l.get_label() for l in lns]
      ax1.legend(lns, labs, loc='best')
  </code></pre>
  
  <p>So how can I add the annotate labels (given by <code>labelString</code>) to my legend?</p>