added return statement sum_of_simplified_exponential_functions

src/main/py/read_math_function.py

@@ -114,4 +114,5 @@ def sum_of_simplified_exponential_functions(type, function):
     if type !="se":
         return False
     summands = function.split('+')
-    simplified = simplify_exponential_function('e', summands)
+    simplified = simplify_exponential_function('e', summands)
+    return simplified