WithItsPiecewiseSumsCombined​(AngouriMath.​Entity)

expr with every sum of piecewises in it combined case by case, as
the evaluator did before an answer's sum of piecewises was left a sum: an integrand
is searched as the one piecewise, and taken apart term by term it was searched once a
term. The sums are written anew, so that no simplification of them is remembered from
outside the scope.
https://github.com/asc-community/AngouriMath/issues/1874