title: Finding max value in a dictionary if two or more keys have same values
body: <p>I have a dictionary say</p>
  
  <pre><code>a = {'2':134,'22':43,'31':134,'29':43}
  </code></pre>
  
  <p>Now using operator package and max function I could easily find the key with max value.
  But that returns only one key(That too the last key if the values of keys are same).</p>
  
  <pre><code>max(a.iteritems(),key=operator.itemgetter(1))[0]
  </code></pre>
  
  <p>How do I return both the keys that has max value.</p>