@@ -149,7 +149,7 @@ def __init__(
 
         self.shuffled = shuffle
         if shuffle:
-            self._dataset.shuffle()
+            self._dataset = self._dataset.shuffle()
 
     def _format_as_dict(self, example):
         input_dict = collections.OrderedDict(
@@ -190,5 +190,5 @@ def __getitem__(self, i):
             ]
 
     def shuffle(self):
-        self._dataset.shuffle()
+        self._dataset = self._dataset.shuffle()
         self.shuffled = True
@@ -104,7 +104,7 @@ def _alter_number(self, num):
         """Helper function of _get_new_number, replace a number with another
         random number within the range of self.max_change."""
         if num not in [0, 2, 4]:
-            change = int(num * self.max_change) + 1
+            change = abs(int(num * self.max_change)) + 1
             if num >= 0:
                 num_list = np.random.randint(max(num - change, 1), num + change, self.n)
             else: