refactoring: simplified by removing unnecessary variable

src/main/py/read_math_function.py

@@ -3,8 +3,7 @@ def read_constant(type, value):
         return False
     if is_string(value):
         if is_allowed_string(type, value):
-            constant = calculate_string(value)
-            return constant
+            return calculate_string(value)
     return value