[
  { cat => 'A', list => [{1, 2, A, 4},{3, 4, A, 5}]}, 
  { cat => 'B', list => [{5, 5, B, 2},{;6, 2, B, 3}]},
  { cat => 'C', list => [{1, 2, C, 2},{2, 3, C, 2},{1, 3, C, 1}]}
]