fixes wrong type in shape argument

python/dune/perftool/pdelab/basis.py

@@ -205,7 +205,7 @@ def evaluate_coefficient_gradient(visitor, element, name, container, restriction
     else:
         temporary_variable(name,
                            shape=(element.cell().geometric_dimension(),),
-                           shape_impl='arr'
+                           shape_impl=('arr',)
                            )
 
     dimindex = component_iname(count=0)