duplicate samples each time they are used

stanza/models/pos/data.py

@@ -1,6 +1,7 @@
 from os import set_inheritable
 import random
 import logging
+import copy
 import torch
 from collections import namedtuple
 
@@ -184,8 +185,11 @@ def __getitem__(self, key):
         pretrained = sample.pretrain
 
         # and deal with char
-        char = [i.copy() for i in sample.char]
-
+        char = copy.deepcopy(sample.char)
+        words = copy.deepcopy(words)
+        xpos = copy.deepcopy(xpos)
+        ufeats = copy.deepcopy(ufeats)
+        pretrained = copy.deepcopy(pretrained)
         raw_text = sample[6]
 
         # mask out the elements that we need to mask out