code: def get_headers(environ):
      
      for key, value in compat.iteritems(environ):
          key = str(key)
          if key.startswith("HTTP_") and key not in ("HTTP_CONTENT_TYPE", "HTTP_CONTENT_LENGTH"):
              yield key[5:].replace("_", "-").lower(), value
          elif key in ("CONTENT_TYPE", "CONTENT_LENGTH"):
              yield key.replace("_", "-").lower(), value
docs: Returns only proper HTTP headers.