title: pandas select rows after groupby
body: <p>In DataFrames, </p>
  
  <pre><code> item_#, status, field1, field2 
     123,    "A",    "val1", "val2"
     223,    "B",    "val3", "val4"
     123,    "B",    "val5", "val6"
     323,    "A",    "val7", "val8"
  </code></pre>
  
  <p>what I want is the list of <code>item_#</code> that has both status <code>"A"</code> and status <code>"B"</code>.
  something like <code>df.groupby('item_#')[(df.status.isin(['A', 'B']</code>), but this doesn't actually work.  It gets me all the item that either one of the values in the list.</p>
  
  <p>any suggestion would be appreciated!</p>