title: deleting rows based on number of true values per group - Python
body: <p>I am trying to delete rows based on groupby and number of True values. 
  Per group, if they have only one true value (sum() = 1), I would like that single row deleted. </p>
  
  <pre><code>import pandas as pd
  df = pd.DataFrame({'id': [1,1,1,2,2,2,3,3,3], 'value': [True, True, False, True, False, False, False, False, True]})
  
  print (df) 
     id  value
  0   1   True
  1   1   True
  2   1  False
  3   2   True
  4   2  False
  5   2  False
  6   3  False
  7   3  False
  8   3   True
  
  df.groupby('id')['value'].sum()
  Out[571]: 
  id
  1    2.0
  2    1.0
  3    1.0
  </code></pre>
  
  <p>id 1 &amp; 3 match the criteria, but how do i delete those single true rows such that the dataframe then becomes:</p>
  
  <pre><code>print (df) 
     id  value
  0   1   True
  1   1   True
  2   1  False
  3   2  False
  4   2  False
  5   3  False
  6   3  False
  </code></pre>