code: def apply(self, docs, clear=True, parallelism=None, progress_bar=True):
          
          super(MentionExtractor, self).apply(
              docs, clear=clear, parallelism=parallelism, progress_bar=progress_bar
          )
docs: Run the MentionExtractor.
  
          :Example: To extract mentions from a set of training documents using
              4 cores::
  
                  mention_extractor.apply(train_docs, parallelism=4)
  
          :param docs: Set of documents to extract from.
          :param clear: Whether or not to clear the existing Mentions
              beforehand.
          :type clear: bool
          :param parallelism: How many threads to use for extraction. This will
              override the parallelism value used to initialize the
              MentionExtractor if it is provided.
          :type parallelism: int
          :param progress_bar: Whether or not to display a progress bar. The
              progress bar is measured per document.
          :type progress_bar: bool