When I try to call any of the Model's aggregate functions (static calls to count, min, max, sum ...) I get this error message from the Builder.

In this example I have a simple class called Characters extending your base model, and its empty (no specialization code). Here is the logged output of the results array from the call to collection->aggregate()

( [errmsg] => no such cmd: aggregate [bad cmd] => Array ( [aggregate] => characters [pipeline] => Array ( [0] => Array ( [$group] => Array ( [_id] => [*] => Array ( [$sum] => 1 ) ) ) ) ) [ok] => 0 )