Add identity_index_map and fix DoubleDict bug#1329

Merged

blegat merged 3 commits intomasterfrom

bl/identity_index_map

May 12, 2021

Commits on May 10, 2021

Add identity_index_map and fix DoubleDict bug
blegat
committed

Commits on May 11, 2021

Move model to first argument
blegat
committed

Commits on May 12, 2021

Document IndexMap and identity_index_map
blegat
committed