title: Find string in multiple columns ?
body: <p>I have a dataframe with 3 columns tel1,tel2,tel3
  I want to keep row that contains a specific value in one or more columns:</p>
  
  <p>For exemple i want to keep row where columns tel1 or tel2 or tel3 start with '06'</p>
  
  <p>How can i do that ?
  Thanks</p>