make plethysm with tensor return result as element of second parent

Author: mantepse

src/sage/combinat/sf/sfa.py

@@ -2879,13 +2879,15 @@ def raise_c(n):
             return lambda c: c.subs(**{str(g): g ** n for g in degree_one})
 
         if tensorflag:
-            tparents = x.parent()._sets
-            return tensor([parent]*len(tparents))(sum(d*prod(sum(raise_c(r)(c)
-                                  * tensor([p[r].plethysm(base(la))
-                                           for (base,la) in zip(tparents,trm)])
-                                  for (trm,c) in x)
-                              for r in mu)
-                       for (mu, d) in p(self)))
+            parent = x.parent()
+            tparents = parent._sets
+            elt = sum(d*prod(sum(raise_c(r)(c)
+                                 * tensor([p[r].plethysm(base(la))
+                                           for (base,la) in zip(tparents, trm)])
+                                 for (trm, c) in x)
+                             for r in mu)
+                      for (mu, d) in p(self))
+            return parent(elt)
 
         # Takes in n, and returns a function which takes in a partition and
         # scales all of the parts of that partition by n