title: How to further filter a data frame after using groupby and value counts
body: <p>I am currently working with a huge data set and I am having some trouble filtering the data. I have a data frame that is something like</p>
  <pre><code>Name  Activity
  John  Cleaning
  Mary  Driving
  Peter Cleaning 
  John  Driving
  </code></pre>
  <p>and so on for a million rows. I applied <code>df.groupby('Name')['activity'].valuecounts()</code> and got a data frame that looks like</p>
  <pre><code>Name  Activity
  John  Cleaning 3
        Driving  2
        Walking  1
  Mary  Cleaning 1
        Driving  1 
        Walking  1
  Peter Cleaning 1
  
  </code></pre>
  <p>I would like to further filter this by extracting only those names that have a maximun value count for activities greater than 1 but I am not sure how to do it. I.e in this example I only want to get John as an output I would appreciate any help</p>