to01 function added

sba.py

@@ -42,10 +42,17 @@ class SBA:
     def __len__(self):
         return self._size
 
+    def to01(self):
+        return "".join([str(self.__getitem__(x)) for x in range(self._size-1, -1, -1)])
+
 if __name__ == "__main__":
     s = SBA(16)
     print(s[1])
     s[1] = 1
     print(s[1])
     print(len(s))
-    print(s[16])
+    try:
+        print(s[16])
+    except Exception as e:
+        print(e)
+    print(s.to01())