title: How to rank over multiple rows and columns (dataframe)
body: <h2>Small sample of data:</h2>
  <pre><code>df = pd.DataFrame({'Customer_ID': [1,1,1,1, 2,2,2,2], 'Customer Age' : [15,15,15,15, 50,50,50,50],   'Similar Customer ID': [5, 8, 11, 15, 22, 28, 31, 11], 'Age': [40, 43, 37, 11, 29, 42, 14, 33],
  })
  </code></pre>
  <h2>Question</h2>
  <p>How do I add a column that rank the customer with related customers, i.e., Customer 1 is 15 years old, I want the desired output to rank that customer as second youngest compared to 'Similar Customer':</p>
  <pre><code>df = pd.DataFrame({'Customer_ID': [1,1,1,1, 2,2,2,2], 'Customer Age' : [15,15,15,15, 50,50,50,50],   'Similar Customer ID': [5, 8, 11, 15, 22, 28, 31, 11], 'Age': [40, 43, 37, 11, 29, 42, 14, 33], 'Age Rank': [2, 2, 2, 2, 5,5,5,5]
  })
  
  </code></pre>