title: Duplicate column A element if designated column is not null
body: <p>I have four columns in my dataframe. Column A is names and Column B, C, and D are language codes designated to names in Column A. I would like to create a combine Column B, C, and D together into one column and have their designated names on the adjacent column. The sample dataframe shall illustrate the operation in a clearer manner. Can anyone please help me on this? Any help is appreciated!!</p>
  <p>Current df</p>
  <pre><code>Name     Language 1     Language 2     Language 3
  one         en             NaN            NaN
  two         ko             ja             zh-CN
  three       fr             de             NaN
  four        nl             ml             NaN
  five        kh             NaN            NaN
  six         hi             en             es
  </code></pre>
  <p>I'm thinking it would be a wide to long operation or some sort.</p>
  <p>Desired output</p>
  <pre><code>Name     Language
  one         en
  two         ko
  two         ja
  two       zh-CN
  three       fr
  three       de
  four        nl
  four        ml
  five        kh
  six         hi
  six         en
  six         es
  </code></pre>
  <p>Thanks again!</p>