transformers

69e16abf - Switch from using sum for flattening lists of lists in group_texts (#14472)

Switch from using sum for flattening lists of lists in group_texts (#14472) * remove sum for list flattening * change to chain(*) * make chain object a list * delete empty lines per sgugger's suggestions Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com> Co-authored-by: Nicholas Broad <nicholas@nmbroad.com> Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>