title: Google Charts hide only some series in legend
body: <p>Is it possible to hide only some series in the legend.</p>
  
  <p>I have a combo chart containing:</p>
  
  <ul>
  <li>amount of A </li>
  <li>amount of B</li>
  <li>amount of C</li>
  </ul>
  
  <p>all displayed as one stacked column.</p>
  
  <p>and also:</p>
  
  <ul>
  <li>amount/second of A</li>
  <li>amount/second of B</li>
  <li>amount/second of C</li>
  </ul>
  
  <p>all displayed as separate lines within the same chart.</p>
  
  <p>Now "amount of A" has the same color as "amount/second of A". This color should be displayed in the legend only once and labelled "A". </p>
  
  <p>Is it possible to do that with Google Charts? If so, how?</p>