Avoid quadratic blowup of memory use and time reading files for DQ han
Avoid O(n^2) number of TMap reads (whose memory is never cleared by ROOT/PyROOT)
Fixes ATLASDQ-953
Edited by Peter Onyisi
Avoid O(n^2) number of TMap reads (whose memory is never cleared by ROOT/PyROOT)
Fixes ATLASDQ-953