code: def check_iterator(iterator):
      # Technically a bytestring is legal, which is why it's a really bad
      # idea, because it may cause the response to be returned
      # character-by-character
      assert_(
          not isinstance(iterator, (str, bytes)),
          "You should not return a string as your application iterator, "
          "instead return a single-item list containing a bytestring.",
      )
  
imports: import re
  import sys
  import warnings
label_desc: Use image node_id 11 for calling a global function with example usage: check_iterator(iterator) without return types