Add auto size support in meaning dataset.

wit/meaning_dataset.py

@@ -256,8 +256,8 @@ class MeaningDataset(Dataset):
         self,
         start,
         end,
-        size,
         vocab_size,
+        size=None,
         max_subitem=10,
         min_subitem=1,
         min_seq_len=2,
@@ -278,7 +278,10 @@ class MeaningDataset(Dataset):
         self.seq_meaning = []
         self.m_height = map.ms_height
         self.m_weight = map.ms_weight
+        if size:
             meanings = np.random.randint(start, end, size=(size))
+        else:
+            meanings = np.arange(start, end)
 
         seq_len = []
         for m in meanings: