code: def _tokenize_wkt(tokens):
      
      negative = False
      for t in tokens:
          if t == '-':
              negative = True
              continue
          else:
              if negative:
                  yield '-%s' % t
              else:
                  yield t
              negative = False
docs: Since the tokenizer treats "-" and numeric strings as separate values,
      combine them and yield them as a single token. This utility encapsulates
      parsing of negative numeric values from WKT can be used generically in all
      parsers.