[cctbxbb] 26-fold symm expansion of asu?

Hi, I'd be grateful for any pointers to clipper or cctbx code that addresses the following: given a "brick" of map grid coordinates that enclose the asu, obtain the 26 symmetry-related "bricks" which contact it. Calculating this by successively generating symmetry mates and testing seems slow; I was wondering whether there was a better way. thank you, Alastair Fyfe UCSC