added function.split for sum_of_simplified_exponential_functions

src/main/py/read_math_function.py

@@ -112,4 +112,5 @@ def simplify_product_function(type, function):
 
 def sum_of_simplified_exponential_functions(type, function):
     if type !="se":
-        return False
+        return False
+    summands = function.split('+')