title: I want to apply group by over a dataframe and filter it throug the mean whose value is greater than any given number
body: <p>In SQL, we apply a filter over aggregated function like below</p>
  
  <pre class="lang-sql prettyprint-override"><code>select col1,avg(col2) as avg_col2 from table group by col1 having avg_col2&gt;100;
  </code></pre>
  
  <p>how can I apply the same logic in pandas over data frame?</p>