A spelling error is fixed

tokenization.py

@@ -361,7 +361,7 @@ def tokenize(self, text):
 
 def _is_whitespace(char):
   """Checks whether `chars` is a whitespace character."""
-  # \t, \n, and \r are technically contorl characters but we treat them
+  # \t, \n, and \r are technically control characters but we treat them
   # as whitespace since they are generally considered as such.
   if char == " " or char == "\t" or char == "\n" or char == "\r":
     return True