title: Finding key(s) with most values in dictionary
body: <p>I'm working on a function where I need to find the keys (of artists names) in a dictionary that have the most values. Sometimes two keys have the same number of values and in that case I need to return a list of the artists names. </p>
  
  <p>Example Dictionary:</p>
  
  <pre><code>{'M':[("One",1400,30.0, 20.5,"oil paint","Austria"),("Three",1430,100.0,102.0,"watercolor","France")],
          'P':[("Eight",1460, 225.0, 200.0, "fresco","Netherlands")],
          'U':[("Nine",1203,182.0, 957.0,"egg tempera","Italy"), ("Twelve",1200,76.2,101.6,"egg tempera","France")]
          }
  </code></pre>
  
  <p>For this dictionary since M and U have the most values (M has 2 and U has 2 while P only has 1) the function should return</p>
  
  <pre><code>artists_with_most_work(dictionary1())
  
  ['M', 'U']
  </code></pre>
  
  <p>How could I search for the number of values of each keys and return the ones that have the most? I figured using max() would be a good idea but I don't think I'm using it correctly in my current attempt below. Thanks to anyone who can help</p>
  
  <p>Code:</p>
  
  <pre><code>def artist_with_most_work(db):
      matches = []
      for key, record_list in db.items():
          for record in record_list:
              if item in record: 
                  max(db) = themax
              matches.append(themax)
          return matches
  </code></pre>