docs: def download_if_missing(self, version=None, verbose=True):
          """Download the jar for version into the jar_filename specified
          in the constructor. Will not overwrite jar_filename if it already
          exists. version defaults to DEFAULT_CORENLP_VERSION (ideally the
          latest but we can't guarantee that since PyStanfordDependencies
          is distributed separately)."""
          if os.path.exists(self.jar_filename):
              return
  
          jar_url = self.get_jar_url(version)
          if verbose:
              print("Downloading %r -> %r" % (jar_url, self.jar_filename))
          opener = ErrorAwareURLOpener()
          opener.retrieve(jar_url, filename=self.jar_filename)