title: Filter values in a dictionary of sets
body: <p>I would like to filter dictionary elements by the values in a list:</p>
  
  <pre><code>s_list = ['blue','white']
  dict_set = {'A':{'red','orange','blue','white'},'B':set(),'C':{'white','green','yellow','blue'},'D':set(),'E':set()}
  </code></pre>
  
  <p>the output for dict_set would be: </p>
  
  <pre><code>dict_set = {'A':{'blue','white'},'B':set(),"C":{'white','blue'},'D':set(),'E':set()}}
  </code></pre>
  
  <p>(Empty sets can be left there, only filter sets that have values)</p>
  
  <p>The implementation I tried to do results in empty sets:</p>
  
  <pre><code>for a,b in dict_set.items():
    dict_set[a] = set([x for x in a if b in s_list])
  </code></pre>