code: def preprocess_gold(self, docs_golds):
          
          for name, proc in self.pipeline:
              if hasattr(proc, "preprocess_gold"):
                  docs_golds = proc.preprocess_gold(docs_golds)
          for doc, gold in docs_golds:
              yield doc, gold
docs: Can be called before training to pre-process gold data. By default,
          it handles nonprojectivity and adds missing tags to the tag map.
  
          docs_golds (iterable): Tuples of `Doc` and `GoldParse` objects.
          YIELDS (tuple): Tuples of preprocessed `Doc` and `GoldParse` objects.