code: def _make_set(var):
      '''
      Force var to be a set
      '''
      if var is None:
          return set()
      if not isinstance(var, list):
          if isinstance(var, six.string_types):
              var = var.split()
          else:
              var = list(var)
      return set(varf _make_set(var):
      '''
      Force var to be a set
      '''
      if var is None:
          return set()
      if not isinstance(var, list):
          if isinstance(var, six.string_types):
              var = var.split()
          else:
              var = list(var)
      return set(var)
docs: Force var to be a set