internal merge of PR #1321

PiperOrigin-RevId: 227918987

Author: cclauss

tensor2tensor/data_generators/text_encoder.py

@@ -78,7 +78,13 @@ def unicode_to_native(s):
 
 
 def is_unicode(s):
-  return isinstance(s, six.text_type)
+  if six.PY2:
+    if isinstance(s, unicode):
+      return True
+  else:
+    if isinstance(s, str):
+      return True
+  return False
 
 
 def to_unicode(s, ignore_errors=False):