title: Subset rows in df depending on conditions
body: <p>Hello I have a df such as :</p>
  
  <p>I wondered how I can subset row where :</p>
  
  <pre><code>COL1 contains a string "ok"
  COL2 &gt; 4
  COL3 &lt; 4 
  </code></pre>
  
  <p>here is an exemple </p>
  
  <pre><code>COL1    COL2 COL3
  AB_ok_7 5    2
  AB_ok_4 2    5
  AB_uy_2 5    2
  AB_ok_2 2    2
  U_ok_7  12   3
  </code></pre>
  
  <p>I should display only :</p>
  
  <pre><code>COL1    COL2 COL3
  AB_ok_7 5    2
  U_ok_7  12   3
  </code></pre>