title: Finding missing comic chapter by Python 3
body: <p>So I have an example of a comic collection database data frame as follow: </p>
  
  <pre><code>  title chapter
  0   A     1
  1   A     2
  2   A     3
  3   A     5
  4   B     2
  5   B     4
  6   B     7
  7   C     3
  8   C     1
  </code></pre>
  
  <p>assuming that the latest chapter available for each title is available at the table above, how to identify the missing chapter for each title with python code? </p>
  
  <pre><code> title chapter
  0   A     4
  1   B     1
  2   B     3
  3   B     5
  4   B     6
  5   C     2 
  </code></pre>
  
  <p>The output of the code is supposed to be able to produce the missing chapters such as the table above (it does not have to be a table, as long as it can find the missing chapter from a comic collection data frame. Thank you for any input and answer. Any help would be appreciated. </p>