title: Difference between pd.merge() and dataframe.merge()
body: <p>I'm wondering what the difference is when you merge by <code>pd.merge</code> versus <code>dataframe.merge()</code>, examples below:</p>
  
  <pre><code>pd.merge(dataframe1, dataframe2)
  </code></pre>
  
  <p>and</p>
  
  <pre><code>dataframe1.merge(dataframe2)
  </code></pre>