Only allow indices that are required by the spec in the array API namespace
Only allow indices that are required by the spec in the array API namespace

The private function _validate_indices describes the cases that are
disallowed. This functionality should be tested (it isn't yet), as the array
API test suite will only test the cases that are allowed, not that
non-required cases are rejected.

numpy/numpy,mattip/numpy,endolith/numpy,anntzer/numpy,mattip/numpy,mhvk/numpy,jakirkham/numpy,mhvk/numpy,endolith/numpy,numpy/numpy,charris/numpy,charris/numpy,mhvk/numpy,mattip/numpy,rgommers/numpy,anntzer/numpy,simongibbons/numpy,endolith/numpy,numpy/numpy,seberg/numpy,mattip/numpy,rgommers/numpy,mhvk/numpy,seberg/numpy,seberg/numpy,jakirkham/numpy,charris/numpy,rgommers/numpy,pdebuyl/numpy,jakirkham/numpy,simongibbons/numpy,charris/numpy,jakirkham/numpy,anntzer/numpy,rgommers/numpy,pdebuyl/numpy,anntzer/numpy,numpy/numpy,pdebuyl/numpy,simongibbons/numpy,mhvk/numpy,pdebuyl/numpy,jakirkham/numpy,seberg/numpy,endolith/numpy,simongibbons/numpy,simongibbons/numpy