code: def add_grist(features):
      """Transform a string by bracketing it with "<>". If already bracketed, does nothing.
      features: one string or a sequence of strings
      return: the gristed string, if features is a string, or a sequence of gristed strings, if features is a sequence
      """
      assert is_iterable_typed(features, basestring) or isinstance(
          features, basestring
      )
  
      def grist_one(feature):
          if feature[0] != "<" and feature[len(feature) - 1] != ">":
              return "<" + feature + ">"
          else:
              return feature
  
      if isinstance(features, str):
          return grist_one(features)
      else:
          return [grist_one(feature) for feature in features]
  
file_path: turicreate/src/external/boost/boost_1_68_0/tools/build/src/util/utility.py
imports: import re
  import os
  import bjam
  from b2.exceptions import *
  from b2.util import is_iterable_typed
label_desc: Use image node_id 3 for calling a global function with example usage: add_grist(features) and returns: grist_one, unknown, unknown, feature