small fix
python code for ```_group_bool_array```
```_group_bool_array``` cythonized
```_group_bool_array``` cythonized (small fix)
_group_bool_array the other way around
_group_bool_array another try
making bool array from index access
Merge branch 'group_bool_array_meth2' into group_bool_array
_group_bool_array another try
_group_bool_array another try :)
clean up
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